[R-sig-Geo] Converting Grid to factor list

[Ronnie Babigumira]

Hi listers
I would like to change a grid to a factor list so as to apply Join Count statistics however when I use
mygrid.f <- factor(mygrid)

I get an error message " 'x' must be atomic".

Looking through the RHelp archives, I have chanced on emails with a similar problem but no direct answer to this. Is 
anyone farmiliar with this and how can I go about it


Many thanks

Ronnie