[R] removing characters from a string

Liaw, Andy andy_liaw at merck.com
Tue Apr 12 15:03:23 CEST 2005

Just gsub() non-numerics with ""; e.g.:

> gsub("[a-zA-Z]", "", "aB9c81")
[1] "981"

[I'm really bad in regular expressions, and don't know how to construct


> From: Vivek Rao
> Is there a simple way in R to remove all characters
> from a string other than those in a specified set? For
> example, I want to keep only the digits 0-9 in a
> string.
> In general, I have found the string handling abilities
> of R a bit limited. (Of course it's great for stats in
> general). Is there a good reference on this? Or should
> R programmers dump their output to a text file and use
> something like Perl or Python for sophisticated text
> processing?
> I am familiar with the basic functions such as nchar,
> substring, as.integer, print, cat, sprintf etc.
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