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Thursday, February 9, 2017

Angular Material - Overview

What is Angular Material?

Angular Material is a UI component library for Angular JS developers. Angular Material's reusable UI components helps in constructing attractive, consistent, and functional web pages and web apps while adhering to modern web design principles like browser portability, device independence, and graceful degradation.

How to Use Angular Material?

There are two ways to use Angular Material:

Local Installation - You can download the Angular Material libraries using npm, jspm, or bower on your local machine and include it in your HTML code.

Angular Material - Autocomplete

md-autocomplete, an Angular Directive, is used as a special input control with an inbuilt drop-down to show all possible matches to a custom query. This control acts as a real-time suggestion box as soon as the user types in the input area.

Angular Material - Bottom Sheet

$mdBottomSheet, an Angular Service, is used to open a bottom sheet over the application and provides a simple promise API.

Methods

S.N.	Method & Description
1	$mdBottomSheet.show(options); Show a bottom sheet with the specified options.

Angular Material - Cards

md-card, an Angular Directive, is a container directive and is used to draw cards in angularjs application. Following are the angular directives and classes used in md-card.

Angular Material - Widgets

Angular Material provide a rich library of UI widgets allows users to have advanced interaction capability with the application.

Layout Directive

layout directive on a container element is used to specify the layout direction for its children. Following are the assignable values:

Angular Material - Inputs

The md-input-container an Angular directive, is a container component to contains any <input> or <textarea> element as a child. md-input-container also supports error handling using the standard ng-messages directives and animates the messages using ngEnter/ngLeave events or the ngShow/ngHide events.

Angular Material - Icons

The md-icon an Angular directive, is a component to show vector-based icons in application. It supports icon fonts and SVG icons also apart from using Google Material Icons.

Angular Material - Grids

The md-grid-list an Angular directive, is a component for laying out content for varying screen sizes. A grid has 12 columns in the desktop size screen, 8 in the tablet size screen, and 4 in the phone size screen, where each size have predefined margins and gutters. Cells are laid out in sequential manner in a row, in the order they are defined.

Angular Material - SideNav

The md-sidenav, an Angular directives is used to show a container component which can be shown or hide programmatically. It slides out over the top of the main content region by default.

Angular Material - Fab Speed Dial

The md-fab-speed-dial an Angular directive, is used to show a series of popup elements or buttons for quick access to common actions.

Attributes

Angular Material - Subheaders

The md-subheader, an Angular directives is used to show a subheader for a section.

Example

The following example showcases the use of md-subheader showcase uses of subheader component.
am_subheaders.htm

<html lang="en" >

Angular Material - Swipe

Swipe functionality is meant for mobile devices. Following directives are used to handle swipes.

md-swipe-down, an Angular directives is used to specify custom behavior when an element is swiped down.
md-swipe-left, an Angular directives is used to specify custom behavior when an element is swiped left.

Angular Material - Switches

The md-switch, an Angular directives is used to show a switch.

Attributes

S.N.	Parameter & Description
1	* ng-model Assignable angular expression to data-bind to.
2	name

Angular Material - Theme

Angular Material Components uses intention group classes like md-primary, md-accent, md-warn and additional classes for color differences like md-hue-1, md-hue-2, or md-hue-3. Following components supports use of above mentioned classes.

Angular Material - Toasts

The Angular Material provides various special methods to show unobtrusive alerts to the users. Angular Material provides a term toast for them and $mdToast service is used to show toasts.

Angular Material - Typography

Angular Material provides various typography CSS classes which can be used to create visual consistency across Angular JS application.

S.N.	Class Name & Description
1	md-display-1 Shows the text with Regular 34px.

md-virtual-repeat-container

md-virtual-repeat-container is the scroll container for the md-virtual-repeat component.

Attributes - md-virtual-repeat-container

S.N.	Parameter & Description
1	md-top-index Binds the index of the item that is at the top of the scroll container to $scope. It can both read and set the scroll position.

Angular Material - WhiteFrame

Angular Material has several special classes to display containers as paper-like cards with shadow.

S.N.	Class Name & Description
1	md-whiteframe-1dp Styles a container for any HTML content with 1px bordered shadow. Adds z-depth of 1.

What is Angular Material?

Angular Material - Useful Resources

If you want to list down your website, book or any other resource on this page then please contact at webmaster@tutorialspoint.com

Angular Material - Discussion

AJAX stands for Asynchronous JavaScript and XML. AJAX is a new technique for creating better, faster, and more interactive web applications with the help of XML, HTML, CSS, and Java Script.
Ajax uses XHTML for content, CSS for presentation, along with Document Object Model and JavaScript for dynamic content display.

AJAX - Technologies

AJAX cannot work independently. It is used in combination with other technologies to create interactive webpages.

JavaScript

Loosely typed scripting language.
JavaScript function is called when an event occurs in a page.
Glue for the whole AJAX operation.

AJAX - Examples

Here is a list of some famous web applications that make use of AJAX.

Google Maps

A user can drag an entire map by using the mouse, rather than clicking on a button.

AJAX - Browser Support

All the available browsers cannot support AJAX. Here is a list of major browsers, that support AJAX.

Mozilla Firefox 1.0 and above.
Netscape version 7.1 and above.
Apple Safari 1.2 and above.

AJAX - Action

This chapter gives you a clear picture of the exact steps of AJAX operation.

Steps of AJAX Operation

A client event occurs.
An XMLHttpRequest object is created.
The XMLHttpRequest object is configured.

AJAX - XMLHttpRequest

The XMLHttpRequest object is the key to AJAX. It has been available ever since Internet Explorer 5.5 was released in July 2000, but was not fully discovered until AJAX and Web 2.0 in 2005 became popular.

AJAX - Database Operations

To clearly illustrate how easy it is to access information from a database using AJAX, we are going to build MySQL queries on the fly and display the results on "ajax.html". But before we proceed, let us do the ground work. Create a table using the following command.

AJAX Security: Server Side

AJAX-based Web applications use the same server-side security schemes of regular Web applications.

AJAX - Issues

AJAX is growing very fast and that is the reason that it contains many issues with it. We hope with the passes of time, they will be resolved and AJAX will become ideal for web applications. We are listing down a few issues that AJAX currently suffers from.

What is AJAX?

AJAX stands for Asynchronous JavaScript and XML. AJAX is a new technique for creating better, faster, and more interactive web applications with the help of XML, HTML, CSS, and Java Script.

AJAX - Useful Resources

The following resources contain additional information on AJAX. Please use them to get more in-depth knowledge on this topic.

Discuss AJAX

AJAX, is a web development technique for creating interactive web applications.
If you know JavaScript, HTML, CSS, and XML, then you need to spend just one hour to start with AJAX.

VBA - Overview

VBA stands for Visual Basic for Applications an event-driven programming language from Microsoft that is now predominantly used with Microsoft office applications such as MSExcel, MS-Word, and MS-Access.
It helps techies to build customized applications and solutions to enhance the capabilities of those applications.

VBA - Excel Macros

In this chapter, you will learn how to write a simple macro in a step by step manner.
Step 1 − First, enable 'Developer' menu in Excel 20XX. To do the same, click File → Options.
Step 2 − Click ‘Customize the Ribbon’ tab and check 'Developer'. Click 'OK'.

VBA - Excel Terms

In this chapter, you will acquaint yourself with the commonly used excel VBA terminologies. These terminologies will be used in further modules, hence understanding each one of these is important.

VBA - Macro Comments

Comments are used to document the program logic and the user information with which other programmers can seamlessly work on the same code in future.

VBA - Message Box

The MsgBox function displays a message box and waits for the user to click a button and then an action is performed based on the button clicked by the user.

VBA - InputBox

The InputBox function prompts the users to enter values. After entering the values, if the user clicks the OK button or presses ENTER on the keyboard, the InputBox function will return the text in the text box. If the user clicks the Cancel button, the function will return an empty string ("").

VBA - Variables

Variable is a named memory location used to hold a value that can be changed during the script execution. Following are the basic rules for naming a variable.

VBA - Constants

Constant is a named memory location used to hold a value that CANNOT be changed during the script execution. If a user tries to change a Constant value, the script execution ends up with an error. Constants are declared the same way the variables are declared.

VBA - Operators

An Operator can be defined using a simple expression - 4 + 5 is equal to 9. Here, 4 and 5 are called operands and + is called operator. VBA supports following types of operators −

VBA - Decisions

Decision making allows the programmers to control the execution flow of a script or one of its sections. The execution is governed by one or more conditional statements.
Following is the general form of a typical decision making structure found in most of the programming languages.

VBA - Loops

There may be a situation when you need to execute a block of code several number of times. In general, statements are executed sequentially: The first statement in a function is executed first, followed by the second, and so on.

VBA - Strings

Strings are a sequence of characters, which can consist of either alphabets, numbers, special characters, or all of them. A variable is said to be a string if it is enclosed within double quotes " ".

VBA - Date-Time Function

VBScript Date and Time Functions help the developers to convert date and time from one format to another or to express the date or time value in the format that suits a specific condition.

VBA - Arrays

We know very well that a variable is a container to store a value. Sometimes, developers are in a position to hold more than one value in a single variable at a time. When a series of values are stored in a single variable, then it is known as an array variable.

VBA - User Defined Functions

A function is a group of reusable code which can be called anywhere in your program. This eliminates the need of writing the same code over and over again. This enables the programmers to divide a big program into a number of small and manageable functions.

VBA - Sub Procedure

Sub Procedures are similar to functions, however there are a few differences.

Sub procedures DO NOT Return a value while functions may or may not return a value.
Sub procedures CAN be called without a call keyword.
Sub procedures are always enclosed within Sub and End Sub statements.

VBA - Events

VBA, an event-driven programming can be triggered when you change a cell or range of cell values manually. Change event may make things easier, but you can very quickly end a page full of formatting. There are two kinds of events.

VBA - Error Handling

There are three types of errors in programming: (a) Syntax Errors, (b) Runtime Errors, and (c) Logical Errors.

Syntax errors

Syntax errors, also called as parsing errors, occur at the interpretation time for VBScript. For example, the following line causes a syntax error because it is missing a closing parenthesis.

VBA - Excel Objects

When programming using VBA, there are few important objects that a user would be dealing with.

Application Objects
Workbook Objects
Worksheet Objects
Range Objects

VBA - Text Files

You can also read Excel File and write the contents of the cell into a Text File using VBA. VBA allows the users to work with text files using two methods −

File System Object
using Write Command

VBA - Programming Charts

Using VBA, you can generate charts based on certain criteria. Let us take a look at it using an example.
Step 1 − Enter the data against which the graph has to be generated.

VBA - User Forms

A User Form is a custom-built dialog box that makes a user data entry more controllable and easier to use for the user. In this chapter, you will learn to design a simple form and add data into excel.

VBA - Quick Guide

VBA - Useful Resources

The following resources contain additional information on VBA. Please use them to get more in-depth knowledge on this topic.

Discuss VBA

VBA stands for Visual Basic for Applications, an event-driven programming language from Microsoft. It is now predominantly used with Microsoft Office applications such as MSExcel, MS-Word and MS-Access. This tutorial teaches the basics of VBA. Each of the sections contain related topics with simple and useful examples.

Wednesday, February 8, 2017

VB.Net - Overview

Visual Basic .NET (VB.NET) is an object-oriented computer programming language implemented on the .NET Framework. Although it is an evolution of classic Visual Basic language, it is not backwards-compatible with VB6, and any code written in the old version does not compile under VB.NET.

VB.Net - Environment Setup

In this chapter, we will discuss the tools available for creating VB.Net applications.
We have already mentioned that VB.Net is part of .Net framework and used for writing .Net applications. Therefore before discussing the available tools for running a VB.Net program, let us understand how VB.Net relates to the .Net framework.

VB.Net - Program Structure

Before we study basic building blocks of the VB.Net programming language, let us look a bare minimum VB.Net program structure so that we can take it as a reference in upcoming chapters.

VB.Net - Basic Syntax

VB.Net is an object-oriented programming language. In Object-Oriented Programming methodology, a program consists of various objects that interact with each other by means of actions. The actions that an object may take are called methods. Objects of the same kind are said to have the same type or, more often, are said to be in the same class.

VB.Net - Data Types

Data types refer to an extensive system used for declaring variables or functions of different types. The type of a variable determines how much space it occupies in storage and how the bit pattern stored is interpreted.

VB.Net - Variables

A variable is nothing but a name given to a storage area that our programs can manipulate. Each variable in VB.Net has a specific type, which determines the size and layout of the variable's memory; the range of values that can be stored within that memory; and the set of operations that can be applied to the variable.

VB.Net - Constants and Enumerations

The constants refer to fixed values that the program may not alter during its execution. These fixed values are also called literals.
Constants can be of any of the basic data types like an integer constant, a floating constant, a character constant, or a string literal. There are also enumeration constants as well.

VB.Net - Modifiers

The modifiers are keywords added with any programming element to give some especial emphasis on how the programming element will behave or will be accessed in the program

VB.Net - Statements

A statement is a complete instruction in Visual Basic programs. It may contain keywords, operators, variables, literal values, constants and expressions.
Statements could be categorized as:

VB.Net - Directives

The VB.Net compiler directives give instructions to the compiler to preprocess the information before actual compilation starts.
All these directives begin with #, and only white-space characters may appear before a directive on a line. These directives are not statements.

VB.Net - Operators

An operator is a symbol that tells the compiler to perform specific mathematical or logical manipulations. VB.Net is rich in built-in operators and provides following types of commonly used operators:

VB.Net - Decision Making

Decision making structures require that the programmer specify one or more conditions to be evaluated or tested by the program, along with a statement or statements to be executed if the condition is determined to be true, and optionally, other statements to be executed if the condition is determined to be false.

VB.Net - Loops

VB.Net - Strings

In VB.Net, you can use strings as array of characters, however, more common practice is to use the String keyword to declare a string variable. The string keyword is an alias for the System.String class.

VB.Net - Date & Time

Most of the softwares you write need implementing some form of date functions returning current date and time. Dates are so much part of everyday life that it becomes easy to work with them without thinking. VB.Net also provides powerful tools for date arithmetic that makes manipulating dates easy.

VB.Net - Arrays

An array stores a fixed-size sequential collection of elements of the same type. An array is used to store a collection of data, but it is often more useful to think of an array as a collection of variables of the same type.
All arrays consist of contiguous memory locations.

VB.Net - Collections

Collection classes are specialized classes for data storage and retrieval. These classes provide support for stacks, queues, lists, and hash tables. Most collection classes implement the same interfaces.

VB.Net - Functions

A procedure is a group of statements that together perform a task when called. After the procedure is executed, the control returns to the statement calling the procedure. VB.Net has two types of procedures:

Functions
Sub procedures or Subs

VB.Net - Sub Procedures

As we mentioned in the previous chapter, Sub procedures are procedures that do not return any value. We have been using the Sub procedure Main in all our examples. We have been writing console applications so far in these tutorials.

VB.Net - Classes & Objects

When you define a class, you define a blueprint for a data type. This doesn't actually define any data, but it does define what the class name means, that is, what an object of the class will consist of and what operations can be performed on such an object.

VB.Net - Exception Handling

An exception is a problem that arises during the execution of a program. An exception is a response to an exceptional circumstance that arises while a program is running, such as an attempt to divide by zero.
Exceptions provide a way to transfer control from one part of a program to another. VB.Net exception handling is built upon four keywords: Try, Catch, Finally and Throw.

VB.Net - File Handling

A file is a collection of data stored in a disk with a specific name and a directory path. When a file is opened for reading or writing, it becomes a stream.
The stream is basically the sequence of bytes passing through the communication path. There are two main streams: the input stream and the output stream.

VB.Net - Basic Controls

An object is a type of user interface element you create on a Visual Basic form by using a toolbox control. In fact, in Visual Basic, the form itself is an object. Every Visual Basic control consists of three important elements:

VB.Net - Dialog Boxes

There are many built-in dialog boxes to be used in Windows forms for various tasks like opening and saving files, printing a page, providing choices for colors, fonts, page setup, etc., to the user of an application. These built-in dialog boxes reduce the developer's time and workload.

VB.Net - Advanced Form

In this chapter, let us study the following concepts:

Adding menus and sub menus in an application
Adding the cut, copy and paste functionalities in a form
Anchoring and docking controls in a form
Modal forms

VB.Net - Event Handling

Events are basically a user action like key press, clicks, mouse movements, etc., or some occurrence like system generated notifications. Applications need to respond to events when they occur.
Clicking on a button, or entering some text in a text box, or clicking on a menu item, all are examples of events. An event is an action that calls a function or may cause another event.

VB.Net - Regular Expressions

A regular expression is a pattern that could be matched against an input text. The .Net framework provides a regular expression engine that allows such matching. A pattern consists of one or more character literals, operators, or constructs.

VB.Net - Database Access

Applications communicate with a database, firstly, to retrieve the data stored there and present it in a user-friendly way, and secondly, to update the database by inserting, modifying and deleting data.
Microsoft ActiveX Data Objects.Net (ADO.Net) is a model, a part of the .Net framework that is used by the .Net applications for retrieving, accessing and updating data.

VB.Net - Excel Sheet

VB.Net provides support for interoperability between the COM object model of Microsoft Excel 2010 and your application.
To avail this interoperability in your application, you need to import the namespace Microsoft.Office.Interop.Excel in your Windows Form Application.

VB.Net - Send Email

VB.Net allows sending e-mails from your application. The System.Net.Mail namespace contains classes used for sending e-mails to a Simple Mail Transfer Protocol (SMTP) server for delivery.
The following table lists some of these commonly used classes:

VB.Net - XML Processing

The Extensible Markup Language (XML) is a markup language much like HTML or SGML. This is recommended by the World Wide Web Consortium and available as an open standard.
The System.Xml namespace in the .Net Framework contains classes for processing XML documents.

VB.Net - Web Programming

A dynamic web application consists of either or both of the following two types of programs:

Server-side scripting - these are programs executed on a web server, written using server-side scripting languages like ASP (Active Server Pages) or JSP (Java Server Pages).

VB.Net - Overview

VB.Net - Useful Resources

The following resources contain additional information on VB.Net. Please use them to get more in-depth knowledge on this topic.

Discuss VB.Net

VB.Net is a simple, modern, object-oriented computer programming language developed by Microsoft to combine the power of .NET Framework and the common language runtime with the productivity benefits that are the hallmark of Visual Basic.

Swift - Overview

Swift is a new programming language developed by Apple Inc for iOS and OS X development. Swift adopts the best of C and Objective-C, without the constraints of C compatibility.

Try it Option Online
We have set up the Swift Programming environment online, so that you can compile and execute all the available examples online. It gives you confidence in what you are reading and enables you to verify the programs with different options. Feel free to modify any example and execute it online.

Swift - Basic Syntax

We have already seen a piece of Swift program while setting up the environment. Let's start once again with the following Hello, World! program created for OS X playground, which includes import Cocoa as shown below −

Swift - Data Types

While doing programming in any programming language, you need to use different types of variables to store information. Variables are nothing but reserved memory locations to store values. This means that when you create a variable, you reserve some space in memory.

Swift - Variables

A variable provides us with named storage that our programs can manipulate. Each variable in Swift has a specific type, which determines the size and layout of the variable's memory; the range of values that can be stored within that memory; and the set of operations that can be applied to the variable.
Swift supports the following basic types of variables −

Swift - Optionals

Swift also introduces Optionals type, which handles the absence of a value. Optionals say either "there is a value, and it equals x" or "there isn't a value at all".
An Optional is a type on its own, actually one of Swift’s new super-powered enums. It has two possible values, None and Some(T), where T is an associated value of the correct data type available in Swift.

Swift - Constants

Constants refer to fixed values that a program may not alter during its execution. Constants can be of any of the basic data types like an integer constant, a floating constant, a character constant, or a string literal. There are enumeration constants as well.

Swift - Literals

A literal is the source code representation of a value of an integer, floating-point number, or string type. The following are examples of literals −

42               // Integer literal
3.14159          // Floating-point literal
"Hello, world!"  // String literal

Swift - Operators

An operator is a symbol that tells the compiler to perform specific mathematical or logical manipulations. Objective-C is rich in built-in operators and provides the following types of operators −

Arithmetic Operators
Comparison Operators
Logical Operators

Swift - Decision Making

Decision making structures require that the programmer specifies one or more conditions to be evaluated or tested by the program, along with a statement or statements to be executed if the condition is determined to be true, and optionally, other statements to be executed if the condition is determined to be false.

Swift - Loops

There may be a situation when you need to execute a block of code several number of times. In general statements are executed sequentially: The first statement in a function is executed first, followed by the second, and so on.

Swift - Strings

Strings in Swift are an ordered collection of characters, such as "Hello, World!" and they are represented by the Swift data type String, which in turn represents a collection of values of Character type.

Swift - Characters

A character in Swift is a single character String literal, addressed by the data type character. Take a look at the following example. It uses two Character constants −

import Cocoa

let char1: Character = "A"
let char2: Character = "B"

Swift - Arrays

Swift arrays are used to store ordered lists of values of the same type. Swift puts strict checking which does not allow you to enter a wrong type in an array even by mistake.

Swift - Dictionaries

Swift dictionaries are used to store unordered lists of values of the same type. Swift puts strict checking which does not allow you to enter a wrong type in a dictionary even by mistake.

Swift - Functions

A function is a set of statements organized together to perform a specific task. A Swift function can be as simple as a simple C function to as complex as an Objective C language function. It allows us to pass local and global parameter values inside the function calls.

Swift - Closures

Closures in Swift are similar to that of self-contained functions organized as blocks and called anywhere like C and Objective C languages. Constants and variable references defined inside the functions are captured and stored in closures. Functions are considered as special cases of closures and it takes the following three forms −

Swift - Enumerations

An enumeration is a user-defined data type which consists of set of related values. Keyword enum is used to defined enumerated data type.

Swift - Structures

Swift provides a flexible building block of making use of constructs as Structures. By making use of these structures once can define constructs methods and properties.

Swift - Classes

Classes in Swift are building blocks of flexible constructs. Similar to constants, variables and functions the user can define class properties and methods. Swift provides us the functionality that while declaring classes the users need not create interfaces or implementation files.

Swift - Properties

Swift language provides properties for class, enumeration or structure to associate values. Properties can be further classified into Stored properties and Computed properties.
Difference between Stored Properties and Computed Properties.

Swift - Methods

In Swift language Functions associated with particular types are referred to as Methods. In Objective C Classes are used to define methods, whereas Swift language provides the user flexibility to have methods for Classes, Structures and Enumerations.

Swift - Subscripts

Accessing the element members of a collection, sequence and a list in Classes, Structures and Enumerations are carried out with the help of subscripts. These subscripts are used to store and retrieve the values with the help of index.

Swift - Inheritance

The ability to take than more form is defined as Inheritance. Generally a class can inherit methods, properties and functionalities from another class. Classes can be further categorized in to sub class and super class.

Sub Class − when a class inherits properties, methods and functions from another class it is called as sub class

Swift - Initialization

Classes, structures and enumerations once declared in Swift are initialized for preparing instance of a class. Initial value is initialized for stored property and also for new instances too the values are initialized to proceed further.

Swift - Deinitialization

Before a class instance needs to be deallocated 'deinitializer' has to be called to deallocate the memory space. The keyword 'deinit' is used to deallocate the memory spaces occupied by the system resources. Deinitialization is available only on class types.

Swift - ARC Overview

Memory management functions and its usage are handled in Swift language through Automatic reference counting (ARC). ARC is used to initialize and deinitialize the system resources thereby releasing memory spaces used by the class instances when the instances are no longer needed.

Swift - Optional Chaining

The process of querying, calling properties, subscripts and methods on an optional that may be 'nil' is defined as optional chaining. Optional chaining return two values −

if the optional contains a 'value' then calling its related property, methods and subscripts returns values.
if the optional contains a 'nil' value all its its related property, methods and subscripts returns nil.

Swift - Type Casting

To validate the type of an instance 'Type Casting' comes into play in Swift language. It is used to check whether the instance type belongs to a particular super class or subclass or it is defined in its own hierarchy.
Swift type casting provides two operators 'is' to check the type of a value and 'as' and to cast the type value to a different type.

Swift - Extensions

Functionality of an existing class, structure or enumeration type can be added with the help of extensions. Type functionality can be added with extensions but overriding the functionality is not possible with extensions.

Swift - Protocols

Protocols provide a blueprint for Methods, properties and other requirements functionality. It is just described as a methods or properties skeleton instead of implementation. Methods and properties implementation can further be done by defining classes, functions and enumerations.

Swift - Generics

Swift language provides 'Generic' features to write flexible and reusable functions and types. Generics are used to avoid duplication and to provide abstraction. Swift standard libraries are built with generics code. Swifts 'Arrays' and 'Dictionary' types belong to generic collections.

Swift - Access Control

To restrict access to code blocks, modules and abstraction is done through access control. Classes, structures and enumerations can be accessed according to their properties, methods, initializers and subscripts by access control mechanisms.

Swift - Quick Guide

Swift is a new programming language developed by Apple Inc for iOS and OS X development. Swift adopts the best of C and Objective-C, without the constraints of C compatibility.

Swift makes use of safe programming patterns.
Swift provides modern programming features.
Swift provides Objective-C like syntax.

Swift - Useful Resources

The following resources contain additional information on Swift. Please use them to get more in-depth knowledge on this.

Discuss Swift

Swift is a new programming language developed by Apple Inc for iOS and OS X development. Swift adopts the best of C and Objective-C, without the constraints of C compatibility. Swift uses the same runtime as the existing Obj-C system on Mac OS and iOS which makes Swift programs run on many existing iOS 6 and OS X 10.8 platforms.

Socket.IO - Overview

Socket.IO

Socket.IO is a JavaScript library for realtime web applications. It enables realtime, bi-directional communication between web clients and servers. It has two parts: a client-side library that runs in the browser, and a server-side library for node.js. Both components have a nearly identical API.

Socket.IO - Environment

To get started with developing using the Socket.IO, you need to have Node and npm(node package manager) installed. If you don’t already have these, head over to Node setup to install node on your local system. Confirm that node and npm are installed by running the following commands in your terminal.

Socket.IO - Hello World

Create a file called app.js and enter the following to set up an express application:

var app = require('express')();
var http = require('http').Server(app);

app.get('/', function(req, res){
  res.sendfile('index.html');
});

Socket.IO - Event Handling

Sockets work based on events. There are some reserved events that can be accessed using the socket object on the server side: connect, message, disconnect, reconnect, ping, join and leave. The client side socket object also provides us with some reserved events: connect, connect_error, connect_timeout, reconnect, etc.

Socket.IO - Broadcasting

Broadcasting means sending a message to all connected clients. Broadcasting can be done at multiple levels. We can send the message to all connected clients, to clients on a namespace and clients in a particular room. The latter 2 would be covered in their respective chapters.

Socket.IO - Namespaces

Socket.IO allows you to “namespace” your sockets, which essentially means assigning different endpoints or paths.
This is a useful feature to minimize the number of resources (TCP connections) and at the same time separate concerns within your application by introducing separation between communication channels.

Socket.IO - Rooms

Within each namespace, you can also define arbitrary channels that sockets can join and leave. These channels are called rooms. Rooms are used to further separate concerns.
Rooms also share the same socket connection like namespaces.

Socket.IO - Error Handling

We've worked on local servers till now which will almost never give us errors related to connections, timeouts, etc. But in real life production environments, handling such errors are of utmost importance. So we'll now discuss how we can handle connection errors on the client side.

Socket.IO - Logging and Debugging

Socket.IO uses a very famous debugging module developed by ExpresJS's main author, called debug.
Earlier socket.IO used to log everything to the console making it quite difficult to actually debug the problem. After the v1.0 release, you can specify what you want to log.

Fallbacks

Socket.IO has a lot of underlying transport mechanisms, which deal with various constraints arising due to cross browser issues, WebSocket implementations, firewalls, port blocking, etc.
Though W3C has a defined specification for WebSocket API, it is still lacking in implementation.

Socket.IO - Chat Application

Now that we are well aquainted with Socket.IO, let us write a chat application which we can use to chat on different chat rooms. We will allow users to choose a username and allow them to chat using them. So first let us set up our HTML file to request for a username:

Socket.IO

Socket.IO - Useful Resources

The following resources contain additional information on Socket.IO. Please use them to get more in-depth knowledge on this topic.

Socket.IO - Discussion

Socket.IO enables real-time bidirectional event-based communication. It works on every platform, browser or device, focusing equally on reliability and speed. Socket.IO is built on top of the WebSockets API(Client side) and Node.js. It is one of the most depended-upon library on npm.

Scala - Overview

Scala, short for Scalable Language, is a hybrid functional programming language. It was created by Martin Odersky. Scala smoothly integrates the features of object-oriented and functional languages. Scala is compiled to run on the Java Virtual Machine.

Try it Option Online
We have set up the Scala Programming environment on-line, so that you can compile and execute all the available examples on line. It gives you confidence in what you are reading and enables you to verify the programs with different options. Feel free to modify any example and execute it on-line.

Scala - Basic Syntax

If you have a good understanding on Java, then it will be very easy for you to learn Scala. The biggest syntactic difference between Scala and Java is that the ';' line end character is optional.

Scala - Data Types

Scala has all the same data types as Java, with the same memory footprint and precision. Following is the table giving details about all the data types available in Scala −

Scala - Variables

Variables are nothing but reserved memory locations to store values. This means that when you create a variable, you reserve some space in memory.
Based on the data type of a variable, the compiler allocates memory and decides what can be stored in the reserved memory.

Scala - Classes & Objects

This chapter takes you through how to use classes and objects in Scala programming. A class is a blueprint for objects. Once you define a class, you can create objects from the class blueprint with the keyword new. Through the object you can use all functionalities of the defined class.

Scala - Access Modifiers

This chapter takes you through the Scala access modifiers. Members of packages, classes or objects can be labeled with the access modifiers private and protected, and if we are not using either of these two keywords, then access will be assumed as public.

Scala - Operators

An operator is a symbol that tells the compiler to perform specific mathematical or logical manipulations. Scala is rich in built-in operators and provides the following types of operators −

Arithmetic Operators
Relational Operators
Logical Operators
Bitwise Operators
Assignment Operators

Scala - IF ELSE Statements

This chapter takes you through the conditional construction statements in Scala programming. Following is the general form of a typical decision making IF...ELSE structure found in most of the programming languages.

Scala - Loop Statements

This chapter takes you through the loop control structures in Scala programming languages.
There may be a situation, when you need to execute a block of code several number of times. In general, statements are executed sequentially: The first statement in a function is executed first, followed by the second, and so on.

Scala - Functions

A function is a group of statements that perform a task. You can divide up your code into separate functions. How you divide up your code among different functions is up to you, but logically, the division usually is so that each function performs a specific task.

Scala - Closures

A closure is a function, whose return value depends on the value of one or more variables declared outside this function.
The following piece of code with anonymous function.

val multiplier = (i:Int) => i * 10

Scala - Strings

This chapter takes you through the Scala Strings. In Scala, as in Java, a string is an immutable object, that is, an object that cannot be modified. On the other hand, objects that can be modified, like arrays, are called mutable objects. Strings are very useful objects, in the rest of this section, we present important methods of java.lang.String class.

Scala - Arrays

Scala provides a data structure, the array, which stores a fixed-size sequential collection of elements of the same type. An array is used to store a collection of data, but it is often more useful to think of an array as a collection of variables of the same type.

Scala - Collections

Scala has a rich set of collection library. Collections are containers of things. Those containers can be sequenced, linear sets of items like List, Tuple, Option, Map, etc. The collections may have an arbitrary number of elements or be bounded to zero or one element (e.g., Option).

Scala - Traits

A trait encapsulates method and field definitions, which can then be reused by mixing them into classes. Unlike class inheritance, in which each class must inherit from just one superclass, a class can mix in any number of traits.

Scala - Pattern Matching

Pattern matching is the second most widely used feature of Scala, after function values and closures. Scala provides great support for pattern matching, in processing the messages.

Scala - Regular Expressions

This chapter explains how Scala supports regular expressions through Regex class available in the scala.util.matching package.
Try the following example program where we will try to find out word Scala from a statement.

Scala - Exception Handling

Scala's exceptions work like exceptions in many other languages like Java. Instead of returning a value in the normal way, a method can terminate by throwing an exception. However, Scala doesn't actually have checked exceptions.

Scala - Extractors

An extractor in Scala is an object that has a method called unapply as one of its members. The purpose of that unapply method is to match a value and take it apart. Often, the extractor object also defines a dual method apply for building values, but this is not required.

Scala - Files I/O

Scala is open to make use of any Java objects and java.io.File is one of the objects which can be used in Scala programming to read and write files.
The following is an example program to writing to a file.

Scala - Overview

Scala - Useful Resources

The following resources contain additional information on Scala. Please use them to get more in-depth knowledge on this topic.

Discuss Scala

Scala is a modern multi-paradigm programming language designed to express common programming patterns in a concise, elegant, and type-safe way.

Rexx - Overview

Rexx (Restructured Extended Executor) is designed to be a scripting language. Its goal is to make scripting as easy, fast, reliable, and error-free as possible. Many programming languages are designed for compatibility with older languages, and are written for specific audiences or platforms.

Try it Option Online
We have set up the Rexx Programming environment on-line, so that you can compile and execute all the available examples on line. It gives you confidence in what you are reading and enables you to verify the programs with different options. Feel free to modify any example and execute it on-line.

Rexx - Installation

The following steps will explain in detail how Rexx can be installed on a Windows system.
Step 1 − Launch the Installer downloaded in the earlier section. After the installer starts, click on the Run button.

Rexx - Installation of Plugin-Ins

In this chapter, we will discuss on how to install plug-ins on popular IDE’s (Integrated Development Environment). Rexx as a programming language is also available in popular IDE’s such as Eclipse. Let’s look at how we can get the required plugin’s in these IDE’s, so that you have more choices in working with Rexx.

Rexx - Basic Syntax

In order to understand the basic syntax of Rexx, let us first look at a simple Hello World program.

Example

/* Main program */ 
say "Hello World"

Rexx - DataTypes

In any programming language, you need to use various variables to store various types of information. Variables are nothing but reserved memory locations to store values. This means that when you create a variable you reserve some space in the memory to store the value associated with that variable.

Rexx - Variables

In Rexx, all variables are bound with the ‘=’ statement. Variable names are sometimes referred to as symbols. They may be composed of Letters, Digits, and Characters such as ‘. ! ? _’. A variable name you create must not begin with a digit or a period. A simple variable name does not include a period. A variable name that includes a period is called a compound variable and represents an array or table.

Rexx - Operators

An operator is a symbol that tells the compiler to perform specific mathematical or logical manipulations.
Rexx has various types of operators which are also explained in detail as follows −

Rexx - Arrays

Arrays in any programming language allow you to group a list of values of the same type. The use of arrays is that it allows you to build a list of similar type of values which are sortable, searchable and can be easily manipulated. Rexx also allows one to define arrays. These arrays can be one dimensional or multidimensional.

Rexx - Loops

So far we have seen statements which have been executed one after the other in a sequential manner. Additionally, statements are provided in Rexx to alter the flow of control in a program’s logic. They are then classified into a flow of control statements which we will study in detail.

Rexx - Decision Making

Decision making structures require that the programmer specify one or more conditions to be evaluated or tested by the program.
The following diagram shows the general form of a typical decision-making structure found in most of the programming languages.

Rexx - Numbers

Rexx has the following data types when it comes to numbers.

Integer − A string of numerics that does not contain a decimal point or exponent identifier. The first character can be a plus (+) or minus (-) sign. The number that is represented must be between -2147483648 and 2147483647, inclusive.

Rexx - Strings

Strings in Rexx are denoted by a sequence of characters. The following program is an example of strings −

/* Main program */ 
a = "This is a string" 
say a

The output of the above program is as follows −

This is a string

Rexx - Functions

The code in Rexx is normally divided into Functions and Subroutines. Using functions helps in segregating the code into many more logical units. Let’s look at these functions in detail.

Rexx - Stacks

The stack is sometimes called the external data queue, but we follow common usage and refer to it as the stack. It is a block of memory that is logically external to Rexx. Instructions like push and queue place data into the stack, and instructions like pull and parse pull extract data from it.

Rexx - File I/O

Rexx provides a number of methods when working with I/O. Rexx provides easier classes to provide the following functionalities for files.

Reading files
Writing to files
Seeing whether a file is a file or directory

Rexx - Functions For Files

In this chapter, we will discuss regarding some of the other functions that are available for files.

S.No.	Functions for Files
1	Lines This function returns either the value 1 or the number of lines left to read in an input stream. The filename is given as the input to the function.

Rexx - Subroutines

In any programming language, the entire program is broken into logical modules. This makes it easier to write code that can be maintained easily. This is a basic requirement for any programming language.
In Rexx, modules can be written using Subroutines and functions. Let’s look at the subroutines in detail.

Rexx - Built-In Functions

Every programming language has some built-in functions that help the programmer do some routine tasks. Rexx also has a lot of built in functions.
Let’s look at all of these functions available in Rexx.

Rexx - System Commands

One of the biggest advantages in Rexx is the ability to create re-usable scripts. Often in organizations nowadays, having re-usable scripts is a big value add in saving time to do common repetitive tasks.
For example, technology teams in an IT organization can have the need to have scripts which do common everyday tasks.

Rexx - XML

XML is a portable, open source language that allows programmers to develop applications that can be read by other applications, regardless of the operating system and/or developmental language. This is one of the most common languages used for exchanging data between applications.

Rexx - Regina

Regina is another Rexx interpreter available to compile and run Rexx programs. The official site for Regina is − www.regina-rexx.sourceforge.net/

Rexx - Parsing

One of the most powerful features of Rexx is its ability to parse text values. You probably will not see this in any other programming languages.
The general format of the parse statement is as follows −

Rexx - Signals

In Rexx, the signal instruction is used generally for two purposes, which are −

One is to transfer control to another part of the program. This is normally like the go-to label which is used in other programming languages.
The other is to go to a specific trap label.

Rexx - Debugging

Debugging is an important feature in any programming language. It helps the developer to diagnose errors, find the root cause and then resolve them accordingly. In Rexx, the trace utility is used for debugging. The trace instruction can be implemented in 2 ways, one is the batch mode and the other is the interactive mode. Let’s look at how to implement both options.

Rexx - Error Handling

Rexx has the ability to also work on Error handling as in other programming languages.
The following are some of the various error conditions that are seen in Rexx.

Rexx - Object Oriented

When you install ooRexx as per the environment chapter, you will also have the ability to work with classes and objects. Please note that all of the following code needs to be run in the ooRexx interpreter. The normal Rexx interpreter will not be able to run this object oriented code.

Rexx - Portability

Portability is an important aspect in any programming language. As one knows, Rexx is available in a variety of operating systems such as Windows and Linux. So it need to be ensured that when one develops a program on the Windows platform, that it has the necessary precautions taken if the same programs runs on a Linux platform.

Rexx - Extended Functions

Rexx provides a number of extended functions that gives a wide variety of functionality, most of them which allow you to interact with the Operating System. Let’s look at some of them in detail as explained below.

Rexx - Instructions

Rexx provides a number of instructions that gives a wide variety of functionality, most of them which allow you to interact with the Operating System. Let’s look at some of them in detail.

Rexx - Implementations

The Rexx language has a lot of various implementations as we have already seen in the previous chapters. Each implementation has its own functionality. Let’s look at the various implementations available for Rexx.

Rexx - Netrexx

NetRexx is the java implementation of Rexx. In NetRexx, the implementer is used to convert the Rexx program to a java program which can then be run on any Java virtual machine.

Rexx - Brexx

BRexx is a lighter weight implementation of Rexx. It still has a lot of functionality to offer as part of the Rexx implementation.

Rexx - Databases

Rexx has the ability to work with a variety of databases which are listed below.

HSQLDB
Oracle
SQL Server
MySQL
MongoDB

Rexx - Handheld & Embedded Programming

Handheld devices have come a long way and Rexx has a lot of ways in which it can run on these devices. Rexx has support for Pocket PC’s, Palm devices, PDA’s and other smart phone devices. The advantage of Rexx to work on these platforms is that Rexx is really a small weight programming system which just runs in the span of a few kilobytes.

Rexx - Performance

One of the key aspects of any programming language is the performance of the application. Special practices need to be taken care of to ensure that the application’s performance is not hampered. Let’s look at some of the considerations described in steps for better understanding −

Rexx - Best Programming Practices

Every programmer wants their program to be the best when it comes to quality and efficiency. The following are some of the best programing practices or hints when writing Rexx programs which can help one achieve these goals.

Hint 1

Use the address command before you issue any command to the operating system or command prompt. This will help you get the address space beforehand in memory and cause your program to run more efficiently.
An example of the address command is shown below.

Example

/* Main program */ 
address system dir

The output of the command is as follows, but it could vary from system to system.

Volume in drive H is Apps 
Volume Serial Number is 8E66-AC3D  
Directory of H:\  
06/30/2016  01:28 AM    <DIR>          Apps 
07/05/2016  03:40 AM               463 main.class 
07/07/2016  01:30 AM                46 main.nrx 
07/07/2016  01:42 AM                38 main.rexx 
3 File(s)            547 bytes 
Dir(s)  313,085,173,760 bytes free

Hint 2

Ensure all commands to the operating system are in upper case and in quotes wherever possible.
An example for the same is shown below.

Example

/* Main program */ 
options arexx_bifs 
say chdir('\REXXML100') 
say directory()

When we run the above program, we will get the following result.

0 
D:\rexxxml100

Hint 3

Avoid creating big comment blocks as shown in the following program.

Example

/******/ 
/* */ 
/* */ 
/* */ 
/******/ 
/* Main program */ 
address system dir

Hint 4

Use the Parse statement to assign default values. An example for the same is shown below.

Example

parse value 0 1 with 
a, 
b

Hint 5

Use the "Left(var1,2)" statement wherever possible instead of the “substr(var1,1,2)" statement.

Hint 6

Use the "Right(var1,2)" statement wherever possible instead of the “substr(var1,length(var1),2)" statement.

Rexx - Graphical User Interface

In order to use the graphic user interfaces available in Rexx, one needs to use 2 packages, one is called ActiveTcl and the other is the Rexxtk package. Along with these 2 packages, one can design normal forms which can have buttons and other controls on the forms.

Rexx - Reginald

Reginald is another Rexx interpreter which was developed by Jeff Glantt and has some customizations on how Rexx programs can be run. In this section, we will see how to get Reginald setup and run a few Rexx programs in it.

Rexx - Web Programming

Rexx has the facility to work with web servers as well. The most common being the apache web server. In order to use Rexxw with the Apache web server, you need to first download the Rexx modules from the following link − https://sourceforge.net/projects/modrexx/?source=typ_redirect
Once done, make sure to add the mod Rexx modules to the class path.

Rexx - Quick Guide

Rexx - Useful Resources

The following resources contain additional information on Rexx. Please use them to get more in-depth knowledge on this.

Discuss Rexx

Rexx (Restructured Extended Executor) is designed to be a scripting language. Its goal is to make scripting as easy, fast, reliable, and error-free as possible. Many programming languages are designed for compatibility with older languages, and are written for specific audiences or platforms. Rexx ignores extraneous objectives.

R - Overview

R is a programming language and software environment for statistical analysis, graphics representation and reporting. R was created by Ross Ihaka and Robert Gentleman at the University of Auckland, New Zealand, and is currently developed by the R Development Core Team.
The core of R is an interpreted computer language which allows branching and looping as well as modular programming using functions. R allows integration with the procedures written in the C, C++, .Net, Python or FORTRAN languages for efficiency.
R is freely available under the GNU General Public License, and pre-compiled binary versions are provided for various operating systems like Linux, Windows and Mac.
R is free software distributed under a GNU-style copy left, and an official part of the GNU project called GNU S.

Evolution of R

R was initially written by Ross Ihaka and Robert Gentleman at the Department of Statistics of the University of Auckland in Auckland, New Zealand. R made its first appearance in 1993.

Try it Option Online
You really do not need to set up your own environment to start learning R programming language. Reason is very simple, we already have set up R Programming environment online, so that you can compile and execute all the available examples online at the same time when you are doing your theory work.

R - Basic Syntax

As a convention, we will start learning R programming by writing a "Hello, World!" program. Depending on the needs, you can program either at R command prompt or you can use an R script file to write your program. Let's check both one by one.

R - Data Types

Generally, while doing programming in any programming language, you need to use various variables to store various information. Variables are nothing but reserved memory locations to store values. This means that, when you create a variable you reserve some space in memory.

R - Variables

A variable provides us with named storage that our programs can manipulate. A variable in R can store an atomic vector, group of atomic vectors or a combination of many Robjects. A valid variable name consists of letters, numbers and the dot or underline characters. The variable name starts with a letter or the dot not followed by a number.

R - Operators

An operator is a symbol that tells the compiler to perform specific mathematical or logical manipulations. R language is rich in built-in operators and provides following types of operators.

R - Decision making

Decision making structures require the programmer to specify one or more conditions to be evaluated or tested by the program, along with a statement or statements to be executed if the condition is determined to be true, and optionally, other statements to be executed if the condition is determined to be false.

R - Loops

There may be a situation when you need to execute a block of code several number of times. In general, statements are executed sequentially. The first statement in a function is executed first, followed by the second, and so on.

R - Functions

A function is a set of statements organized together to perform a specific task. R has a large number of in-built functions and the user can create their own functions.

R - Strings

Any value written within a pair of single quote or double quotes in R is treated as a string. Internally R stores every string within double quotes, even when you create them with single quote.

R - Vectors

Vectors are the most basic R data objects and there are six types of atomic vectors. They are logical, integer, double, complex, character and raw.

R - Lists

Lists are the R objects which contain elements of different types like − numbers, strings, vectors and another list inside it. A list can also contain a matrix or a function as its elements. List is created using list() function.

R - Matrices

Matrices are the R objects in which the elements are arranged in a two-dimensional rectangular layout. They contain elements of the same atomic types. Though we can create a matrix containing only characters or only logical values, they are not of much use.

R - Arrays

Arrays are the R data objects which can store data in more than two dimensions. For example − If we create an array of dimension (2, 3, 4) then it creates 4 rectangular matrices each with 2 rows and 3 columns. Arrays can store only data type.

R - Factors

Factors are the data objects which are used to categorize the data and store it as levels. They can store both strings and integers. They are useful in the columns which have a limited number of unique values. Like "Male, "Female" and True, False etc. They are useful in data analysis for statistical modeling.

R - Data Frames

A data frame is a table or a two-dimensional array-like structure in which each column contains values of one variable and each row contains one set of values from each column.
Following are the characteristics of a data frame.

R - Packages

R packages are a collection of R functions, complied code and sample data. They are stored under a directory called "library" in the R environment. By default, R installs a set of packages during installation. More packages are added later, when they are needed for some specific purpose.

R - Data Reshaping

Data Reshaping in R is about changing the way data is organized into rows and columns. Most of the time data processing in R is done by taking the input data as a data frame.

R - CSV Files

In R, we can read data from files stored outside the R environment. We can also write data into files which will be stored and accessed by the operating system. R can read and write into various file formats like csv, excel, xml etc.

R - Excel File

Microsoft Excel is the most widely used spreadsheet program which stores data in the .xls or .xlsx format. R can read directly from these files using some excel specific packages. Few such packages are - XLConnect, xlsx, gdata etc. We will be using xlsx package. R can also write into excel file using this package.

R - Binary Files

A binary file is a file that contains information stored only in form of bits and bytes.(0’s and 1’s). They are not human readable as the bytes in it translate to characters and symbols which contain many other non-printable characters. Attempting to read a binary file using any text editor will show characters like Ø and ð.

R - XML Files

XML is a file format which shares both the file format and the data on the World Wide Web, intranets, and elsewhere using standard ASCII text. It stands for Extensible Markup Language (XML). Similar to HTML it contains markup tags. But unlike HTML where the markup tag describes structure of the page, in xml the markup tags describe the meaning of the data contained into he file.

R - JSON Files

JSON file stores data as text in human-readable format. Json stands for JavaScript Object Notation. R can read JSON files using the rjson package.

R - Web Data

Many websites provide data for consumption by its users. For example the World Health Organization(WHO) provides reports on health and medical information in the form of CSV, txt and XML files. Using R programs, we can programmatically extract specific data from such websites.

R - Databases

The data is Relational database systems are stored in a normalized format. So, to carry out statistical computing we will need very advanced and complex Sql queries. But R can connect easily to many relational databases like MySql, Oracle, Sql server etc. and fetch records from them as a data frame.

R - Pie Charts

R Programming language has numerous libraries to create charts and graphs. A pie-chart is a representation of values as slices of a circle with different colors. The slices are labeled and the numbers corresponding to each slice is also represented in the chart.

R - Bar Charts

A bar chart represents data in rectangular bars with length of the bar proportional to the value of the variable. R uses the function barplot() to create bar charts. R can draw both vertical and horizontal bars in the bar chart. In bar chart each of the bars can be given different colors.

R - Boxplots

Boxplots are a measure of how well distributed is the data in a data set. It divides the data set into three quartiles. This graph represents the minimum, maximum, median, first quartile and third quartile in the data set. It is also useful in comparing the distribution of data across data sets by drawing boxplots for each of them.

R - Histograms

A histogram represents the frequencies of values of a variable bucketed into ranges. Histogram is similar to bar chat but the difference is it groups the values into continuous ranges. Each bar in histogram represents the height of the number of values present in that range.

R - Line Graphs

A line chart is a graph that connects a series of points by drawing line segments between them. These points are ordered in one of their coordinate (usually the x-coordinate) value. Line charts are usually used in identifying the trends in data.

R - Scatterplots

Scatterplots show many points plotted in the Cartesian plane. Each point represents the values of two variables. One variable is chosen in the horizontal axis and another in the vertical axis.
The simple scatterplot is created using the plot() function.

R - Mean, Median & Mode

Statistical analysis in R is performed by using many in-built functions. Most of these functions are part of the R base package. These functions take R vector as an input along with the arguments and give the result.
The functions we are discussing in this chapter are mean, median and mode.

R - Linear Regression

Regression analysis is a very widely used statistical tool to establish a relationship model between two variables. One of these variable is called predictor variable whose value is gathered through experiments. The other variable is called response variable whose value is derived from the predictor variable.

R - Multiple Regression

Multiple regression is an extension of linear regression into relationship between more than two variables. In simple linear relation we have one predictor and one response variable, but in multiple regression we have more than one predictor variable and one response variable.

R - Logistic Regression

The Logistic Regression is a regression model in which the response variable (dependent variable) has categorical values such as True/False or 0/1. It actually measures the probability of a binary response as the value of response variable based on the mathematical equation relating it with the predictor variables.

R - Normal Distribution

In a random collection of data from independent sources, it is generally observed that the distribution of data is normal. Which means, on plotting a graph with the value of the variable in the horizontal axis and the count of the values in the vertical axis we get a bell shape curve.

R - Binomial Distribution

The binomial distribution model deals with finding the probability of success of an event which has only two possible outcomes in a series of experiments. For example, tossing of a coin always gives a head or a tail.

R - Poisson Regression

Poisson Regression involves regression models in which the response variable is in the form of counts and not fractional numbers. For example, the count of number of births or number of wins in a football match series. Also the values of the response variables follow a Poisson distribution.

R - Analysis of Covariance

We use Regression analysis to create models which describe the effect of variation in predictor variables on the response variable. Sometimes, if we have a categorical variable with values like Yes/No or Male/Female etc. The simple regression analysis gives multiple results for each value of the categorical variable.

R - Time Series Analysis

Time series is a series of data points in which each data point is associated with a timestamp. A simple example is the price of a stock in the stock market at different points of time on a given day. Another example is the amount of rainfall in a region at different months of the year.

R - Nonlinear Least Square

When modeling real world data for regression analysis, we observe that it is rarely the case that the equation of the model is a linear equation giving a linear graph. Most of the time, the equation of the model of real world data involves mathematical functions of higher degree like an exponent of 3 or a sin function.

R - Decision Tree

Decision tree is a graph to represent choices and their results in form of a tree. The nodes in the graph represent an event or choice and the edges of the graph represent the decision rules or conditions. It is mostly used in Machine Learning and Data Mining applications using R.

R - Random Forest

In the random forest approach, a large number of decision trees are created. Every observation is fed into every decision tree. The most common outcome for each observation is used as the final output. A new observation is fed into all the trees and taking a majority vote for each classification model.

R - Survival Analysis

Survival analysis deals with predicting the time when a specific event is going to occur. It is also known as failure time analysis or analysis of time to death. For example predicting the number of days a person with cancer will survive or predicting the time when a mechanical system is going to fail.

R - Chi Square Test

Chi-Square test is a statistical method to determine if two categorical variables have a significant correlation between them. Both those variables should be from same population and they should be categorical like − Yes/No, Male/Female, Red/Green etc.

R - Interview Questions

Dear readers, these R Interview Questions have been designed specially to get you acquainted with the nature of questions you may encounter during your interview for the subject of R programming. As per my experience good interviewers hardly plan to ask any particular question during your interview, normally questions start with some basic concept of the subject and later they continue based on further discussion and what you answer −

R - Overview

R - Useful Resources

The following resources contain additional information on R Programming. Please use them to get more in-depth knowledge on this topic.

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Pascal - Overview

Pascal is a general-purpose, high-level language that was originally developed by Niklaus Wirth in the early 1970s. It was developed for teaching programming as a systematic discipline and to develop reliable and efficient programs.

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We have set up the Pascal Programming environment online, so that you can compile and execute all the available examples online. It gives you confidence in what you are reading and enables you to verify the programs with different options. Feel free to modify any example and execute it online.

Pascal - Program Structures

Before we study basic building blocks of the Pascal programming language, let us look a bare minimum Pascal program structure so that we can take it as a reference in upcoming chapters.

Pascal - Basic Syntax

You have seen a basic structure of pascal program, so it will be easy to understand other basic building blocks of the pascal programming language.

Pascal - Data Types

Data types of an entity indicates the meaning, constraints, possible values, operations, functions and mode of storage associated with it.
Integer, real, Boolean and character types are referred as standard data types. Data types can be categorized as scalar, pointer and structured data types. Examples of scalar data types are integer, real, Boolean, character, subrange and enumerated. Structured data types are made of the scalar types; for example, arrays, records, files and sets. We will discuss the pointer data types later.

Pascal Data Types

Pascal data types can be summarized as below in the following diagram −

Type Declarations

The type declaration is used to declare the data type of an identifier. Syntax of type declaration is −

 type-identifier-1, type-identfier-2 = type-specifier;

For example, the following declaration defines the variables days and age as integer type, yes and true as Boolean type, name and city as string type, fees and expenses as real type.

type
days, age = integer;
yes, true = boolean;
name, city = string;
fees, expenses = real;

Integer Types

Following table gives you details about standard integer types with its storage sizes and value ranges used in Object Pascal −

Type	Minimum	Maximum	Format
Integer	-2147483648	2147483647	signed 32-bit
Cardinal	0	4294967295	unsigned 32-bit
Shortint	-128	127	signed 8-bit
Smallint	-32768	32767	signed 16-bit
Longint	-2147483648	2147483647	signed 32-bit
Int64	-2^63	2^63 - 1	signed 64-bit
Byte	0	255	unsigned 8-bit
Word	0	65535	unsigned 16-bit
Longword	0	4294967295	unsigned 32-bit

Constants

Use of constants makes a program more readable and helps to keep special quantities at one place in the beginning of the program. Pascal allows numerical, logical, string and character constants. Constants can be declared in the declaration part of the program by specifying the const declaration.
Syntax of constant type declaration is follows −

const
Identifier = contant_value;

Following are some examples of constant declarations −

VELOCITY_LIGHT = 3.0E=10;
PIE = 3.141592;
NAME = 'Stuart Little';
CHOICE = yes;
OPERATOR = '+';

All constant declarations must be given before the variable declaration.

Enumerated types

Enumerated data types are user-defined data types. They allow values to be specified in a list. Only assignment operators and relational operators are permitted on enumerated data type. Enumerated data types can be declared as follows −

type
enum-identifier = (item1, item2, item3, ... )

Following are some examples of enumerated type declarations −

type
SUMMER = (April, May, June, July, September);
COLORS = (Red, Green, Blue, Yellow, Magenta, Cyan, Black, White);
TRANSPORT = (Bus, Train, Airplane, Ship);

The order in which the items are listed in the domain of an enumerated type defines the order of the items. For example, in the enumerated type SUMMER, April comes before May, May comes before June, and so on. The domain of enumerated type identifiers cannot consist of numeric or character constants.

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