[R] coplot has me stumped

[Stuart Luppescu]

I'm having trouble with coplot. I have two conditioning variables, and when I
try to specify two sets of given.values, no matter what I do I get the message,
Error: Object "b.levels" not found.

Here is the section of code:
c.ranges <- co.intervals(schses, number=4, overlap=0)
a.ranges <- co.intervals(as.factor(aa94), number=2, overlap=0)
PredAA <- as.factor(aa94)
coplot(Adj.Math.Productivity ~ size94|schses * PredAA, panel=points.lines,
given.values=list(c.ranges, a.ranges ), rows=2, columns=4 )

Instead of 'a.ranges' in the coplot statement, I have also tried c(0,1), and
lots of other variations, but no matter what I do, I always get the same
message. There must be something fundamental I'm missing, but what is it?

I'm using R version 0.63.2 on Linux (intel). I tried to find 0.63.3, but it
doesn't seem to have shown up on the ftp sites yet. Thanks for your help.
______________________________________________________________________
Stuart Luppescu         -=-=-  University of Chicago
ºÍʸ ¤ÈÃÒÆàÈþ¤ÎÉã(EUC)  -=-=-  s-luppescu at uchicago.edu
http://www.consortium-chicago.org/people/sl/sl.html
       ICQ #21172047  AIM: psycho7070
"Being against torture ought to be sort of a bipartisan thing."
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