Retrieve regular expression groups
There are quite a few examples in (1) ?strapply, (2) on the home page and (3) in the vignette (4) on r-help back posts if you having problems with understanding the textual description. Note that X and FUN are also arguments to sapply
args(sapply)
function (X, FUN, ..., simplify = TRUE, USE.NAMES = TRUE) NULL so the sapply construct in your post has the effect of applying c to tmp, pats and strapply so the output you observe is correct. The sapply command never even calls strapply. On Sun, May 2, 2010 at 8:20 PM, OKB (not okblacke)
<brenbarn at brenbarn.net> wrote:
Gabor Grothendieck wrote:
The strapply function in gsubfn does that. ?See http://gsubfn.googlecode.com
? ? ? ?Ah, thanks. ?The documentation for that function is pretty difficult to grasp, but I think I figured it out. . . almost. ?However, for some reason I can't seem to make strapply work inside an sapply (to do multiple regex searches over the same data). ?For instance, take a look at this toy setup.
pats
[1] "([^ ]+) .i. ([^ ]+)" "([^ ]+) ..g ([^ ]+)"
tmp
[1] "this is a big test" ? "this is a pig test" ? "this is a lim test" "this is a non test" ? "this is a big foolio" [6] "this is a wig foolio" "this is a fog test" ? "this is a bog test" ? ? ? ?With these data, strapply(tmp, pats[1], c) works as expected, as does strapply(tmp, pats[2], c). ?However, this doesn't work: sapply(pats, strapply, X=tmp, FUN=c) Instead it returns a strange table, some of whose elements contain the code of strapply itself. ?Also, the above code gives different results depending on whether I specify "X=tmp" or simply "tmp" as the third argument. ?Shouldn't these be the same, since X is the first argument of strapply? ?Any idea what's going on here? Thanks again, -- --OKB (not okblacke) Brendan Barnwell "Do not follow where the path may lead. ?Go, instead, where there is no path, and leave a trail." ? ? ? ?--author unknown
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