retrieve text inside tags in R

Question

I'm trying to retrieve information from a text file that contains tags, eg:

<name> Joe </name>

The text file consists of multiple lines some with more of these tags (eg for height and weight) and some with just other text. I refer to the text file as "sheet" (see code below).

I would like to retrieve the text between the tags. I have come up with the following solution to do so:

m1 <- regexpr("<name> [a-zA-Z]+ </name>", sheet)
m2 <- regmatches(sheet,m1)
m3 <- gsub("<name> ", "", gsub(" </name>", "", m2))
m3

I have not worked with regular expressions before, but I was wondering whether I am not taking a detour with my 'regmatches'. It seems there should be a more direct way to retrieve text inside tags?

Thanks,

Richard

Answer 1

You could do this with one gsub call. Therefore you have create a group by surrounding your pattern by ( and ) . This group could be accessed with a number \\\\1 (backreferences), eg:

sheet <- "<name>foobar</name>"
gsub(pattern="<name>([a-zA-Z]+)</name>", replacement="\\1", x=sheet)
# [1] "foobar"

But as @DieterMenne suggests you should try the XML package for HTML (it supports XPath ):

library("XML")
doc <- xmlParse("<html><name>foobar</name></html>")
xpathSApply(doc, "//name", xmlValue)
# [1] "foobar"

retrieve text inside tags in R

Question

1 answers

solution1
4 ACCPTED 2013-08-11 15:06:42

retrieve text inside tags in R

Question

1 answers

solution1 4 ACCPTED 2013-08-11 15:06:42

solution1
4 ACCPTED 2013-08-11 15:06:42