Hi Jannis,
just use the backreferences in gsub, see ?gsub, -> replacement
test <- c('filename_1_def.pdf', 'filename_2_abc.pdf')
gsub(".*_([A-z]+)\\.pdf", "\\1", test)
hth.
Am 05.10.2011 13:56, schrieb Jannis:
> Dear list memebers,
>
>
> I am stuck with using regular expressions.
>
>
> Imagine I have a vector of character strings like:
>
> test <- c('filename_1_def.pdf', 'filename_2_abc.pdf')
>
> How could I use regexpressions to extract only the 'def'/'abc' parts of these
> strings?
>
>
> Some try from my side yielded no results:
>
> testresults <- grep('(?<=filename_[[:digit:]]_).{1,3}(?=.pdf)', perl = TRUE,
> value = TRUE)
>
> Somehow I seem to miss some important concept here. Until now I always used
> nested sub expressions like:
>
> testresults <- sub('.pdf$', '', sub('^filename_[[:digit:]]_', '' , test))
>
>
> but this tends to become cumbersome and I was wondering whether there is a
> more elegant way to do this?
>
>
>
> Thanks for any help
>
> Jannis
>
>
>
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