On May 20, 2011, at 11:57 AM, Kang Min wrote:
> Hi all,
>
> I'm trying to subset a pattern in a vector. Each argument has 6
> letters, and I need those that start with Z and end with Z.
>
> e.g.
> x <- c("ZFHSJK",
"ZFHJKZ","ZIOPWE","ZLKJSD","ZKFLPZ")
>
> I've looked up other discussions but still can't seem to find the
> answer.
You may need to study the regex page a bit longer
the "^" is the beginning of a string
".+" will math can arbitrarily long string of anything
and "$" indicates the end of a string
> x <- c("ZFHSJK",
"ZFHJKZ","ZIOPWE","ZLKJSD","ZKFLPZ")
> grep("^Z.+Z$", x)
[1] 2 5
> grep("^Z.+Z$", x, value=TRUE)
[1] "ZFHJKZ" "ZKFLPZ"
>
> Thanks.
> Kangmin
>
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David Winsemius, MD
West Hartford, CT