[R] Using grep() to subset lines of text

[Gabor Grothendieck]

Try this:

> a <- 2:3
> b <- c("aaa 2 aaa", "2 aaa", "3 aaa", "aaa 3 aaa")
>
> re <- paste("^(", paste(a, collapse = "|"), ")", sep = "")
> re
[1] "^(2|3)"
> grep(re, b, value = TRUE)
[1] "2 aaa" "3 aaa"

On Sat, Nov 29, 2008 at 7:00 AM, ppaarrkk <simon_ecc at yahoo.co.uk> wrote:
>
> I have two vectors, a and b. b is a text file. I want to find in b those
> elements of a which occur at the beginning of the line in b. I have the
> following code, but it only returns a value for the first value in a, but I
> want both. Any ideas please.
>
>
> a = c(2,3)
>
> b = NULL
> b[1] = "aaa 2 aaa"
> b[2] = "2 aaa"
> b[3] = "3 aaa"
> b[4] = "aaa 3 aaa"
>
> grep(paste("^",a, sep=""), b )
>
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