R XML File

XML stands for Extensible Markup Language (XML), which is designed for data transmission and storage.

If you are not familiar with XML, you can refer to: XML Tutorial

To read and write XML files in R, you need to install an extension package. You can install it by entering the following command in the R console:

install.packages("XML", repos = "https://mirrors.ustc.edu.cn/CRAN/")

To check if the installation was successful:

> any(grepl("XML", installed.packages()))
[1] TRUE

Create a sites.xml file, with the XML file and test script in the same directory, the code is as follows:

Example

<sites>
    <site>
        <id>1</id>
        <name>Google</name>
        <url>www.google.com</url>
        <likes>111</likes>
    </site>

    <site>
        <id>2</id>
        <name>tutorialpro</name>
        <url>www.tutorialpro.org</url>
        <likes>222</likes>
    </site>

    <site>
        <id>3</id>
        <name>Taobao</name>
        <url>www.taobao.com</url>
        <likes>333</likes>
    </site>
</sites>

Next, we can use the XML package to load the XML file data:

Example

# Load the XML package
library("XML")

# Set the file name
result <- xmlParse(file = "sites.xml")

# Output the result
print(result)

To count the amount of XML data:

Example

# Load the XML package
library("XML")

# Set the file name
result <- xmlParse(file = "sites.xml")

# Extract the root node
rootnode <- xmlRoot(result)

# Count the data size
rootsize <- xmlSize(rootnode)

# Output the result
print(rootsize)

Executing the above code outputs:

[1] 3

To view node data, use [ ] for a specific row, and [[ ]] for a specified row and column:

Example

# Load the XML package
library("XML")

# Set the file name
result <- xmlParse(file = "sites.xml")

# Extract the root node
rootnode <- xmlRoot(result)

# View the data of the 2nd node
print(rootnode[2])

# View the 1st data of the 2nd node
print(rootnode[[2]][[1]])

# View the 3rd data of the 2nd node
print(rootnode[[2]][[3]])

Executing the above code outputs:

$site
<site>
  <id>2</id>
  <name>tutorialpro</name>
  <url>www.tutorialpro.org</url>
  <likes>222</likes>
</site> 

attr(,"class")
[1] "XMLInternalNodeList" "XMLNodeList"        
<id>2</id> 
<url>www.tutorialpro.org</url>

Convert XML to Data List

The above outputs are in XML format. We can use the xmlToList() function to convert the file data to a list format, making it easier to read:

Example

# Load the XML package
library("XML")

# Set the file name
result <- xmlParse(file = "sites.xml")

# Convert to list
xml_data <- xmlToList(result)

print(xml_data)
print("============================")

# Output the data of the 1st row, 2nd column
print(xml_data[[1]][[2]])

Executing the above code outputs:

$site
$site$id
[1] "1"

$site$name
[1] "Google"

$site$url
[1] "www.google.com"

$site$likes
[1] "111"


$site
$site$id
[1] "2"

$site$name

[1] "tutorialpro"

$site$url [1] "www.tutorialpro.org"

$site$likes [1] "222"

$site $site$id [1] "3"

$site$name [1] "Taobao"

$site$url [1] "www.taobao.com"

$site$likes [1] "333"

[1] "============================" [1] "Google"