[R] Aggregate drops empty subsets
andrewr at uidaho.edu
Wed Apr 14 16:29:29 CEST 2004
Greetings, R community.
I am trying to create a multi-dimensional contingency table suitable
for analysis by glm() using the poisson family. I have three factors,
each with four levels, with some observed zeros. I'm trying to use
aggregate to construct my contingency table, but it drops empty
subsets, so the zeros get lost. I also tried tapply() but it doesn't
carry over the main effects, just the interactions. I also tried
constructing a new factor from the interactions and merging it with
the contingency table but then I lost the main effects.
Very small example: from the following dataframe
I would want to distill
burn age burn.age count
low young low.young 2
high young high.young 0
low old low.old 1
high old high.old 1
with a solution scaleable to many dimensions.
Is there any easy way to get around this problem?
Thanks for any suggestions,
Andrew Robinson Ph: 208 885 7115
Department of Forest Resources Fa: 208 885 6226
University of Idaho E : andrewr at uidaho.edu
PO Box 441133 W : http://www.uidaho.edu/~andrewr
Moscow ID 83843 Or: http://www.biometrics.uidaho.edu
No statement above necessarily represents my employer's opinion.
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