[R] search for string insider a string

[Gabor Grothendieck]

Try this.  We use regexpr to get the positions and
strapply puts the values in list s.  The unlist statement
converts NULL to NA and simplifies the list, s, to a
numeric vector.  For more info on strapply see
http://gsubfn.googlecode.com

library(gsubfn)  # strapply

x <- c"test1", "bcdtestblabla2.1bla", "cdtestblablabla3.88blabla")

dtest.info <- cbind(posn = regexpr("dtest", x),
   value = { s <- strapply(x, "dtest[^0-9]*([0-9][0-9.]*)", as.numeric)
                unlist(ifelse(sapply(s, length), s, NA))
})

> # the above may be sufficient but
> # if its important to NA out rows with no match add
> dtest.info[dtest.info[,1] < 0,] <- NA
> dtest.info
     pos value
[1,]  NA    NA
[2,]   3  2.10
[3,]   2  3.88

Why do you want the position?   Is there a further transformation needed?
What is it?  There may be even easier approaches to the entire problem.

On Fri, Mar 13, 2009 at 12:25 PM, Tan, Richard <RTan at panagora.com> wrote:
> Hi, sorry if it is a too stupid question, but how do I a string search
> in R:
>
> I have a dataframe A with A$test like:
>
> test1
> bcdtestblabla2.1bla
> cdtestblablabla3.88blabla
>
> and I want to search for string that start with 'dtest' and ends with
> number and return the location of that substring and the number, so the
> end result would be:
>
> NA    NA
> 3    2.1
> 2    3.88
>
> I find grep can probably do this but I am new to the function so would
> like a good example.
>
> Thanks,
> Richard
>
>
>
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>
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