[R] Regular expression help

[William Dunlap]

> x <- "f 147/1315/587 2820/1320/587 3624/1321/587 1852/1322/587"
> gsub("(^| *)([^/ ]*/?){0,2}", "\\1", x)
[1] " 587 587 587 587"
> y <- "aa aa/ aa/bb aa/bb/ aa/bb/cc aa/bb/cc/ aa/bb/cc/dd aa/bb/cc/dd/"
> gsub("(^| *)([^/ ]*/?){0,2}", "\\1", y)
[1] "    cc cc/ cc/dd cc/dd/"


Bill Dunlap
TIBCO Software
wdunlap tibco.com

On Mon, Oct 9, 2017 at 8:02 AM, Duncan Murdoch <murdoch.duncan at gmail.com>
wrote:

> I have a file containing "words" like
>
>
> a
>
> a/b
>
> a/b/c
>
> where there may be multiple words on a line (separated by spaces).  The a,
> b, and c strings can contain non-space, non-slash characters. I'd like to
> use gsub() to extract the c strings (which should be empty if there are
> none).
>
> A real example is
>
> "f 147/1315/587 2820/1320/587 3624/1321/587 1852/1322/587"
>
> which I'd like to transform to
>
> " 587 587 587 587"
>
> Another real example is
>
> "f 1067 28680 24462"
>
> which should transform to "   ".
>
> I've tried a few different regexprs, but am unable to find a way to say
> "transform words by deleting everything up to and including the 2nd slash"
> when there might be zero, one or two slashes.  Any suggestions?
>
> Duncan Murdoch
>
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