How to get a specific node value in R

Question

How do I access value of a particular node of an XML file using R? I am new to R and would also like to know why xmltop[[1]]$IP returns a null. What am I doing wrong?

library('XML')
xmlfile <- xmlTreeParse("E:\\R Scripts\\Data\\Ipdata.xml")
xmltop = xmlRoot(xmlfile)
xmltop[[1]]$IP    # return a null value
xmlValue(xmltop[[1]]$IP)    # returns NA

XML:

<Response>
<location>
 <IP>213.139.122.103</IP>
 <CountryCode>FR</CountryCode>
 <CountryName>France</CountryName>
 <RegionCode/>
 <RegionName/>
 <City/>
 <ZipCode/>
 <TimeZone>Europe/Paris</TimeZone>
 <Latitude>48.86</Latitude>
 <Longitude>2.35</Longitude>
 <MetroCode>0</MetroCode>
 </location>
 <location>
 <IP>213.139.122.102</IP>
 <CountryCode>INR</CountryCode>
 <CountryName>India</CountryName>
 <RegionCode/>
 <RegionName/>
 <City/>
 <ZipCode/>
 <TimeZone>Chennai</TimeZone>
 <Latitude>48.83</Latitude>
 <Longitude>2.34</Longitude>
 <MetroCode>0</MetroCode>
 </location>
</Response>

xml2 is pretty nice for parsing, though you'll need your XPath skills. If you want the text contents of all <IP> nodes, library(xml2) ; xml %>% read_xml() %>% xml_find_all('//IP') %>% xml_text() where xml is the XML text or a path to the file. — alistaire
– alistaire, Commented May 17, 2016 at 5:17
@kumar Did my answer resolve your query? If yes, then accept and upvote. — khrm
– khrm, Commented May 17, 2016 at 7:59
xmltop[[1]][["IP"]] won't give you IP only. It will give you node. — khrm
– khrm, Commented May 17, 2016 at 7:59

zyurnaidi · Accepted Answer · 2016-05-17 05:24:46Z

1

You can access it by this command:

xmltop[[1]][["IP"]]

Even better, you can try to use XPATH through xpathApply or xpathSApply command to access all IP tags:

xpathApply(xmltop, "//IP")

Then you can extract information from these nodes with functions such as xmlValue:

xpathApply(xmltop, "//IP", xmlValue)

EDIT: You need to modify your original code a litte bit (convert the objects into XMLInternalNode) to use the functions such as xmlValue as follow:

xmlfile <- xmlTreeParse("Ipdata.xml", useInternalNodes = T)

answered May 17, 2016 at 5:24

zyurnaidi

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1 Comment

kumar Over a year ago

Thanks it was very helpfull

khrm · Accepted Answer · 2016-05-17 08:05:56Z

1

It can be access usingxmltop[[1]][[1]][[1]] or xmlValue(xmltop[[1]][[1]]) or xmltop[[1]][["IP"]][1]$text. These aren't name according to the nodes.

I would recommend you to convert it to dataframe or list using this code

Data frame:

xmldataframe <- xmlToDataFrame("E:\\R Scripts\\Data\\Ipdata.xml", stringsAsFactors=FALSE)

xmldataframe$IP[1]

List:

xmllist <- xmlToList("E:\\R Scripts\\Data\\Ipdata.xml")

xmllist[[1]]$IP

edited May 17, 2016 at 8:05

answered May 17, 2016 at 4:24

khrm

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2 Comments

kumar Over a year ago

Thanks it was very helpful if I could I would mark both as answers.

khrm Over a year ago

@kumar Welcome. But you can upvote atleast my answer as mine answer was first.

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