Re: [R] Re gular Expression help

From: Wacek Kusnierczyk <>
Date: Sat, 08 Nov 2008 23:02:31 +0100

Gabor Grothendieck wrote:
> For the problem at hand I think I would use your solution
> which is both easily understood and fastest. On the
> other hand the tapply based solutions are coordinate
> free (i.e. no explicit mucking with indices) and readily
> generalize to more than 2 groups -- just replace [^pq] with
> [^pqr], say.

for sure, mine was optimized towards the case, not towards generalizability. the gsubfn one is a loser, though.

but the first one *is* easily generalizable, e.g.,

letters = "pqrs"
sapply(sprintf("^[^%s]*%s", letters, unlist(strsplit(letters, split=""))), grep, x=x, value=TRUE)

while an order of magnitude faster than the tapply ones.

vQ mailing list PLEASE do read the posting guide and provide commented, minimal, self-contained, reproducible code. Received on Sat 08 Nov 2008 - 22:05:24 GMT

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