[R] Find value in vector (or matrix)

[Pascal A. Niklaus]

Hi all,

Is there a function to check if a particular value is contained in a 
vector? I've looked at grep in the hope that I could use a Perl-like 
syntax, but obviously it's different...

I'd like to do something like:

    y <- c("a","b","c")
    if("a" in y)
    {
          # "a" is not in y
    }

Also, is there a way to generate character sequences similar to numeric 
sequences, e.g. something like "A":"J" ? I remember having seen a 
command doing this somewhere, but can't find it anymore

Thanks

Pascal