[R] replace a whole word with sub()

[Prof Brian Ripley]

Do you want to replace the whole word or the whole string?  If the 
latter, use

sub("^Ig.*", "0", x)

(Matching is greedy, so .* matches are many characters as possible, 
here the rest of the string.)

If 'whole word', we need a precise definition of word, but

sub("^Ig\\w*", "0", x)

is one conventional one (a word is alphanumeric: but you might not 
allow numbers).

On Fri, 13 Nov 2009, Giulio Di Giovanni wrote:

> Dear all,
>
> I cannot figure out how to solve a small problem (well, not for me), 
> surely somebody can help me in few seconds.
>
> I have a series of strings in a vector X of the type "xxx", "yyy", 
> "zzz", "IgA", "IgG", "kkk", "IgM", "aaa".
>
> I want to substitute every ENTIRE string beginning with "Ig" with "0".
>
> So, I'd like to have "xxx", "yyy", "zzz", "0", "0", "kkk", "0", "aaa".
>
> I can easily identify these strings with grep("^Ig", X), but if I 
> use this criterion in the sub() function (sub("^Ig", "0", X) I 
> obviously get "0A", "0G" etc.
>
> I didn't expect to do it in this way and I tried with metacharacters 
> and regexps in order to grep and substitute the whole word (\b \>, 
> $). I don't post here my tryings, because they were obviously wrong.
>
> Please can you help me?
>
>
>
> Giulio
>
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-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
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