[R] return value for grep

[David Winsemius]

On Oct 30, 2010, at 10:51 PM, Ulrich wrote:

> Hi,
>
> is it possible to easily change the return value for the grep  
> function for cases where there is no match, for example the value 0  
> or "No" instead of integer (0) )?
>

Seems like is should be  pretty easy. Test for length(grep(...)) == 0  
or equivalently !length(grep(...))

 > gvec <- function(patt, x) sapply (x, function(y) if ( ! 
length(grep(patt, y)) ) {"No"} else {grep(patt, y)} )
 > gvec("b", c("abc", "abc\n"))
   abc abc\n
     1     1
 > gvec("\n", c("abc", "abc\n"))
   abc abc\n
  "No"   "1"

-- 

David Winsemius, MD
West Hartford, CT