R help - Aug 2009 - find numbers in a line with letters

hi,

is there an easy way to extract numbers from a string?

for example I have;
"this Item costs 3.32 Dollars"

is there an easy way to extract the 3.32 as a number?


thanks!

Try this:

library(gsubfn)
s <- "this item costs 3.32 Dollars"
strapply(s, "[0-9][0-9.]*", as.numeric)[[1]]

See http://gsubfn.googlecode.com for more info.

On Wed, Aug 26, 2009 at 6:38 PM, Martin Batholdy<batholdy at
googlemail.com> wrote:
> hi,
>
> is there an easy way to extract numbers from a string?
>
> for example I have;
> "this Item costs 3.32 Dollars"
>
> is there an easy way to extract the 3.32 as a number?
>
>
> thanks!
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

Hi,

On Aug 26, 2009, at 6:38 PM, Martin Batholdy wrote:
> hi,
>
> is there an easy way to extract numbers from a string?
>
> for example I have;
> "this Item costs 3.32 Dollars"
>
> is there an easy way to extract the 3.32 as a number?
Regular expressions to the rescue?

Perhaps you'll need to fine tune it, but see here:

R> gregexpr("(\\d+(\\.\\d+)?)", "this Item costs 3.32
Dollars", perl=T)
[[1]]
[1] 17
attr(,"match.length")
[1] 4

R> gregexpr("(\\d+(\\.\\d+)?)", "this Item costs 3.32 Dollars,
that
item costs 10.12 dollars", perl=T)
[[1]]
[1] 17 47
attr(,"match.length")
[1] 4 5

R> gregexpr("(\\d+(\\.\\d+)?)", "this Item costs 3.32 Dollars,
that
item costs 10 dollars even, ", perl=T)
[[1]]
[1] 17 47
attr(,"match.length")
[1] 4 2

R> gregexpr("(\\d+(\\.\\d+)?)", "this one is free ",
perl=T)
[[1]]
[1] -1
attr(,"match.length")
[1] -1

HTH,
-steve

--
Steve Lianoglou
Graduate Student: Computational Systems Biology
   |  Memorial Sloan-Kettering Cancer Center
   |  Weill Medical College of Cornell University
Contact Info: http://cbio.mskcc.org/~lianos/contact