Displaying 1 result from an estimated 1 matches for "stems139".
2011 Feb 08
1
Grouping by factors in R
...ategories/factors - most importantly, I want to group things so that I
see results by "SizeClass" and then by "Species". This is pretty easy
in SAS using the "Group By" command, but in R, I haven't figured it out.
I've tried using the following code:
> stems139GLM <- glm(Stems ~ Time | SizeClass | Species,
family=poisson, data=stems139)
but R gives me this message:
Error in pmax(exp(eta), .Machine$double.eps) :
cannot mix 0-length vectors with others
In addition: Warning messages:
1: In Ops.factor(Time, SizeClass) : | not meaningful for factors
2...