[R] Must be obvious but not to me : problem with regular expression

Ptit_Bleu ptit_bleu at yahoo.fr
Mon Dec 17 15:34:50 CET 2007


I have a vector called nfichiers of 138 names of file whose extension is .P0
or P1 ... to P8.
The script is not the same when the extension is P0 or P(1 to 8).

Examples of file names :
[128] "Output0.P0"       
[129] "Output0.P1"       
[130] "Output0.P2"       
[131] "Output01102007.P0"
[132] "Output01102007.P1"
[133] "Output01102007.P2"
[134] "Output01102007.P3"
[135] "Output01102007.P4"

To extract the names of file with .P0 extension I wrote :
nfichiers[grep(".P0", nfichiers)]
For the other extensions :
nfichiers[grep(".P[^0]", nfichiers)]

But for the last, I get a length of 138 that is the length of the initial
vector although I have 130 files with .P0 extension.

So I tried "manually" with a small vector :
> s
[1] "aa.P0" "bb.P0" "cc.P1" "dd.P2"
> s[grep(".P[^0]", s)]
[1] "cc.P1" "dd.P2"

It works !!!

Has someone an idea to solve this small problem ?
Thanks in advance,
Ptit Bleu.

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