May 12, 2021 R language tutorial
XML is a file format that uses standard ASCII text to share file formats and data on the World Wide Web, intranet and elsewhere. I t represents the Extensable Markup Language (XML). S imilar to HTML, it contains tag tags. H owever, unlike tag tags in HTML that describe the structure of a page, in xml, tag tags describe the meaning of the data contained in the file.
You can use the "XML" package to read xml files in the R language. T his package can be installed using the following commands.
install.packages("XML")
Create an XMl file by copying the following data into a text editor, such as Note book. Use .xml file extension to save the file and select the file type for 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>
The xml file is read by the R language using the function xmlParse(). It is stored as a list in the R language.
# 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 code above, it produces the following results -
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
# 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 code above, it produces the following results -
output [1] 8
Let's look at the first record of the parsing file. I t will give us an idea of the various elements that exist in the top 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 code above, it produces the following results -
$EMPLOYEE 1 Rick 623.3 1/1/2012 IT attr(,"class") [1] "XMLInternalNodeList" "XMLNodeList"
# 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 code above, it produces the following results -
1 IT Michelle
In order to process the data efficiently in large files, we read the data in the xml file as a data frame. T he data frames are then processed 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 code above, it produces the following results -
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 Finance
Since data can now be used as data frames, we can use data frame-related functions to read and manipulate files.