[R] Problem with the grep function

[Jan_Svatos@eurotel.cz]

Hi Julie,

match is not exactly what you need, as it works with regular expressions 
and takes anything what includes a letter "b".
For your case, there is perfectly suitable

which(nom=="b")

nom <- c("a","b","ab", "b")
which(nom=="b")
[1] 2 4

Jan


- - - Original message: - - -
From: r-help-bounces at stat.math.ethz.ch
Send: 8.7.2004 9:24:58
To: r-help at stat.math.ethz.ch
Subject: [R] Problem with the grep function

Let me present to you my problem :

I have a character vector x and I would like to  obtain the indices of the
elements of
this vector that yielded exactly a match.

For example,  x=nom, pattern="b", I would to obtain 2 because "b" is on 
the
second position.

First program :
nom <- c("a","b","ab")
grep("b",nom)
2 3

Then I try the option extended =FALSE (instead of TRUE by default) and I
obtain '2 3' a second time.

Please can you help me : How can I obtain only 2 in using the grep 
function
(without using the match function).

Thanks you

Julie AUBERT

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