R-alpha: glm cont.

Jim Lindsey jlindsey@luc.ac.be
Wed, 12 Nov 1997 14:16:12 +0100 (MET)


Here is a quick example that the uncorrected glm cannot fit. Suppose
that freq contains the nine values from a 3x3 contingency table, fac1
and fac2 the factor variables indexing the margins, and lin1 and lin2
the corresponding linear variables. Then without my correction, glm
cannot fit 
glm(freq~fac1+fac2+fac1:lin2+fac2:lin1,family=poisson)
because there are 11 variable combinations (3 aliased) and only 9
observations.
  Jim
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