extract all numbers from a string

Hi all,

I have been beating my head against this problem for a bit, but I 
can't figure it out.

I have a series of strings of variable length, and each will have 
one or more numbers, of varying format.  E.g., I might have:


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"

How could I get R to just give me a list of numerics containing the 
numbers therein?

Thanks very much to the regexp wizards!

Cheers,
Nick



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HI,
One way would be:

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"
pattern<- "(\\d)+|(\\d+\\.\\d+)|(-\\d+\\.\\d+)|(\\d+.\\d+e\\d+)|(\\d+\\.\\d+e-\\d+)"
str_extract_all(tmpstr,pattern)[[1]]
#[1] "32"         "32.1"       "0.3523e10"  "0.3523e-10" "-313.1"
  as.numeric(str_extract_all(tmpstr,pattern)[[1]])
A.K.



----- Original Message -----
From: Nick Matzke <matzke at berkeley.edu>
To: R-help at r-project.org
Cc:
Sent: Sunday, June 16, 2013 1:06 AM
Subject: [R] extract all numbers from a string

Hi all,

I have been beating my head against this problem for a bit,
but I can't figure it out.

I have a series of strings of variable length, and each will
have one or more numbers, of varying format.  E.g., I might
have:


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"

How could I get R to just give me a list of numerics
containing the numbers therein?

Thanks very much to the regexp wizards!

Cheers,
Nick

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]])

library(gsubfn)
pat <- "[-+.e0-9]*\\d"
strapplyc(tmpstr, pat)[[1]]

strapply(tmpstr, pat, as.numeric)[[1]]

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

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