[R] Problem with the grep function

[Wolski]

Hi!

For exact matches you can use
== or is.element.
To get the indices use which.

e.g. ==

> x<-c("a","b","ab")
> x=="a"
[1]  TRUE FALSE FALSE
> which((x=="a")==T)
[1] 1

or

e.g. is.element

> is.element(x,"a")
[1]  TRUE FALSE FALSE
> which(is.element(x,"a")==TRUE)
[1] 1
> 

Sincerely
Eryk


*********** REPLY SEPARATOR  ***********

On 7/8/2004 at 9:20 AM aubert at inapg.fr wrote:

>>>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
>>>
>>>______________________________________________
>>>R-help at stat.math.ethz.ch mailing list
>>>https://www.stat.math.ethz.ch/mailman/listinfo/r-help
>>>PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html



Dipl. bio-chem. Eryk Witold Wolski    @    MPI-Moleculare Genetic   
Ihnestrasse 63-73 14195 Berlin       'v'    
tel: 0049-30-83875219               /   \    
mail: wolski at molgen.mpg.de        ---W-W----    http://www.molgen.mpg.de/~wolski