[R] help with dealing with integer(0) returns from grep used within a conditional loop

[Allan Engelhardt]

On 04/07/09 18:56, Mark Kimpel wrote:
> I am using grep to locate colnames to automate a report build and have
> run into a problem when a colname is not found. The use of integer(0)
> in a conditional statement seems to be a no no as it has length 0.
> Below is a self-contained trivial example. I would like to get
> something like "NA" or -1 for the position when it is not found OR
> learn a way to use integer(0) or some "cast" of it in a logical
> statement. Example, output, and sessionInfo follow. Thanks, Mark
>
> ####################################3
> vec.1<- c("a", "b", "c")
> vec.2<- c("a", "c", "d")
> for (i in 1:length(vec.1)){
>    for (j in 1:length(vec.2)){
>      print(paste("i:", i, " j:", j, sep = ""))
>      pos<- grep(vec.1[i], vec.2[j])
>      if (pos>  0){
>    
Try: if ( length(pos) > 0 ) {

Allan.