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

[Uwe Ligges]

ppaarrkk 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 )
> 


grep(paste("^", a, collapse = "|", sep = ""), b)

Uwe Ligges