# [R] extract all numbers from a string

Nick Matzke matzke at berkeley.edu
Mon Jun 17 08:31:20 CEST 2013

```Ooh, nice! Thanks!
Nick

On 6/16/13 8:42 PM, Gabor Grothendieck wrote:
> On Sun, Jun 16, 2013 at 9:00 PM, Nick Matzke <matzke at berkeley.edu> wrote:
>> Thanks *VERY* much, this is great!
>>
>> I realized a few more cases, I think I've got something that covers all the
>> possibilities now:
>>
>>
>>
>> library(stringr)
>> tmpstr = "The first number is: 32.  Another one is: 32.1. Here's a number in
>> scientific format, 0.3523e10, and another, 0.3523e-10, and a negative,
>> -313.1"
>>
>> patternslist = NULL
>> p=0
>> patternslist[[(p=p+1)]] = "(\\d+)"                              # positive
>> integer
>> patternslist[[(p=p+1)]] = "(-\\d+)"                             # negative
>> integer
>> patternslist[[(p=p+1)]] = "(\\d+\\.\\d+)"               # positive float
>> patternslist[[(p=p+1)]] = "(\\d+\\.\\d+e\\d+)"  # positive float, scientific
>> w. positive power
>> patternslist[[(p=p+1)]] = "(\\d+\\.\\d+e-\\d+)" # positive float, scientific
>> w. negative power
>> patternslist[[(p=p+1)]] = "(-\\d+\\.\\d+)"              # negative float
>> patternslist[[(p=p+1)]] = "(-\\d+\\.\\d+e\\d+)" # negative float, scientific
>> w. positive power
>> patternslist[[(p=p+1)]] = "(-\\d+\\.\\d+e-\\d+)"# negative float, scientific
>> w. negative power
>>
>> patternslist[[(p=p+1)]] = "(\\d+e\\d+)"                 # positive int,
>> scientific w. positive power
>> patternslist[[(p=p+1)]] = "(\\d+e-\\d+)"                # positive int,
>> scientific w. negative power
>> patternslist[[(p=p+1)]] = "(-\\d+e\\d+)"                # negative int,
>> scientific w. positive power
>> patternslist[[(p=p+1)]] = "(-\\d+e-\\d+)"               # negative int,
>> scientific w. negative power
>>
>> pattern = paste(patternslist, collapse="|", sep="")
>> pattern
>> as.numeric(str_extract_all(tmpstr,pattern)[[1]])
>>
>> # A more complex string
>> tmpstr = "The first number is: 32.  342 342.1   -3234e-10 3234e-1 Another
>> one is: 32.1. Here's a number in scientific format, 0.3523e10, and another,
>> 0.3523e-10, and a negative, -313.1"
>> #pattern =
>> "(\\d)+|(-\\d)+|(\\d+\\.\\d+)|(-\\d+\\.\\d+)|(\\d+.\\d+e\\d+)|(\\d+\\.\\d+e-\\d+)|(-\\d+.\\d+e\\d+)|(-\\d+\\.\\d+e-\\d+)"
>> as.numeric(str_extract_all(tmpstr,pattern)[[1]])
>
> This much simpler single pattern may be good enough:
>
>> library(gsubfn)
>> pat <- "[-+.e0-9]*\\d"
>> strapplyc(tmpstr, pat)[[1]]
> [1] "32"         "342"        "342.1"      "-3234e-10"  "3234e-1"
> [6] "32.1"       "0.3523e10"  "0.3523e-10" "-313.1"
>> strapply(tmpstr, pat, as.numeric)[[1]]
> [1]  3.200e+01  3.420e+02  3.421e+02 -3.234e-07  3.234e+02  3.210e+01  3.523e+09
> [8]  3.523e-11 -3.131e+02
>
> --
> Statistics & Software Consulting
> GKX Group, GKX Associates Inc.
> tel: 1-877-GKX-GROUP
> email: ggrothendieck at gmail.com
>

--
====================================================
Nicholas J. Matzke

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