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.
You can read a xml file in R using the "XML" package. This package can be installed using following command.
You can read a xml file in R using the "XML" package. This package can be installed using following command.
install.packages("XML")
Input Data
Create a XMl file by copying the below data into a text editor like notepad. Save the file with a .xml extension and choosing the file type as all files(*.*).<RECORDS> <EMPLOYEE> <ID>1</ID> <NAME>Rick</NAME> <SALARY>623.3</SALARY> <STARTDATE>1/1/2012</STARTDATE> <DEPT>IT</DEPT> </EMPLOYEE> <EMPLOYEE> <ID>2</ID> <NAME>Dan</NAME> <SALARY>515.2</SALARY> <STARTDATE>9/23/2013</STARTDATE> <DEPT>Operations</DEPT> </EMPLOYEE> <EMPLOYEE> <ID>3</ID> <NAME>Michelle</NAME> <SALARY>611</SALARY> <STARTDATE>11/15/2014</STARTDATE> <DEPT>IT</DEPT> </EMPLOYEE> <EMPLOYEE> <ID>4</ID> <NAME>Ryan</NAME> <SALARY>729</SALARY> <STARTDATE>5/11/2014</STARTDATE> <DEPT>HR</DEPT> </EMPLOYEE> <EMPLOYEE> <ID>5</ID> <NAME>Gary</NAME> <SALARY>843.25</SALARY> <STARTDATE>3/27/2015</STARTDATE> <DEPT>Finance</DEPT> </EMPLOYEE> <EMPLOYEE> <ID>6</ID> <NAME>Nina</NAME> <SALARY>578</SALARY> <STARTDATE>5/21/2013</STARTDATE> <DEPT>IT</DEPT> </EMPLOYEE> <EMPLOYEE> <ID>7</ID> <NAME>Simon</NAME> <SALARY>632.8</SALARY> <STARTDATE>7/30/2013</STARTDATE> <DEPT>Operations</DEPT> </EMPLOYEE> <EMPLOYEE> <ID>8</ID> <NAME>Guru</NAME> <SALARY>722.5</SALARY> <STARTDATE>6/17/2014</STARTDATE> <DEPT>Finance</DEPT> </EMPLOYEE> </RECORDS>
Reading XML File
The xml file is read by R using the function xmlParse(). It is stored as a list in R.# Load the package required to read XML files. library("XML") # Also load the other required package. library("methods") # Give the input file name to the function. result <- xmlParse(file = "input.xml") # Print the result. print(result)When we execute the above code, it produces the following result −
1 Rick 623.3 1/1/2012 IT 2 Dan 515.2 9/23/2013 Operations 3 Michelle 611 11/15/2014 IT 4 Ryan 729 5/11/2014 HR 5 Gary 843.25 3/27/2015 Finance 6 Nina 578 5/21/2013 IT 7 Simon 632.8 7/30/2013 Operations 8 Guru 722.5 6/17/2014 Finance
Get Number of Nodes Present in XML File
# Load the packages required to read XML files. library("XML") library("methods") # Give the input file name to the function. result <- xmlParse(file = "input.xml") # Exract the root node form the xml file. rootnode <- xmlRoot(result) # Find number of nodes in the root. rootsize <- xmlSize(rootnode) # Print the result. print(rootsize)When we execute the above code, it produces the following result −
output [1] 8
Details of the First Node
Let's look at the first record of the parsed file. It will give us an idea of the various elements present in the top level node.# Load the packages required to read XML files. library("XML") library("methods") # Give the input file name to the function. result <- xmlParse(file = "input.xml") # Exract the root node form the xml file. rootnode <- xmlRoot(result) # Print the result. print(rootnode[1])When we execute the above code, it produces the following result −
$EMPLOYEE 1 Rick 623.3 1/1/2012 IT attr(,"class") [1] "XMLInternalNodeList" "XMLNodeList"
Get Different Elements of a Node
# Load the packages required to read XML files. library("XML") library("methods") # Give the input file name to the function. result <- xmlParse(file = "input.xml") # Exract the root node form the xml file. rootnode <- xmlRoot(result) # Get the first element of the first node. print(rootnode[[1]][[1]]) # Get the fifth element of the first node. print(rootnode[[1]][[5]]) # Get the second element of the third node. print(rootnode[[3]][[2]])When we execute the above code, it produces the following result −
1 IT Michelle
XML to Data Frame
To handle the data effectively in large files we read the data in the xml file as a data frame. Then process the data frame for data analysis.# Load the packages required to read XML files. library("XML") library("methods") # Convert the input xml file to a data frame. xmldataframe <- xmlToDataFrame("input.xml") print(xmldataframe)When we execute the above code, it produces the following result −
ID NAME SALARY STARTDATE DEPT 1 1 Rick 623.30 2012-01-01 IT 2 2 Dan 515.20 2013-09-23 Operations 3 3 Michelle 611.00 2014-11-15 IT 4 4 Ryan 729.00 2014-05-11 HR 5 NA Gary 843.25 2015-03-27 Finance 6 6 Nina 578.00 2013-05-21 IT 7 7 Simon 632.80 2013-07-30 Operations 8 8 Guru 722.50 2014-06-17 FinanceAs the data is now available as a dataframe we can use data frame related function to read and manipulate the file.
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