how to use the return value of function grep in R

Question

I want to use the return value of function grep, I just want to judge whether the var_name has the var I want:

> res<-grep(y,var_name,fixed=FALSE)
> res
integer(0)
> (res==integer(0))
logical(0)
> (res==NULL)
logical(0)

But it is always logical(0), is there any way I can solve this problem

Answer 1

You can try:

if(length(res)==0)
{
    # some code
}

Or directly:

grepl(y, var_name)

Example:

y='dog'
var_name='I am a cat'
# grepl(y, var_name)
#[1] FALSE