On 07-Aug-07 04:20:27, Shao wrote:
> Hi,everyone.
>
> I have a problem when using the grep.
> for example:
> a <- c("aa","aba","abac")
> b<- c("ab","aba")
>
> I want to match the whole word,so
> grep("^aba$",a)
> it returns 2
>
> but when I used it a more useful way:
> grep("^b[2]$",a),
> it doesn't work at all, it can't find it, returning integer(0).
>
> How can I chang the format in the second way?
>
> Thanks.
>
> --
> Shao
The problem is that in the string "^b[2]$" the element b[2] of b
is not evaluated, but simply the successive characters ^ b [ 2 ] $
are passed to grep as a character string, which of course is not
found. You can construct a character string with the value of b[2]
in it by using paste():
grep(paste("^",b[2],"$",sep=""),a)
[1] 2
Ted.
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E-Mail: (Ted Harding) <[EMAIL PROTECTED]>
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Date: 07-Aug-07 Time: 07:43:14
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