[R] Ancova doesn't return test statistics
Johan A. Stenberg
johan.stenberg at emg.umu.se
Thu Nov 15 16:36:13 CET 2007
I'm quite sure that this is a stupid question, but I'll ask anyway.
I want to perform an ANCOVA with two continuous factors and three
Plant population growth rate (GR) = dependent variable
Seed reduction due to herbivory (SR) = continuous explanatory variable
Herbivore species (HS, 2 levels) = categorical explanatory variable
Population (Pop, 24 levels) = categorical explanatory variable
Population size (Popsize) = continuous explanatory variable
Year (Year, 16 levels) = categorical explanatory variable
My model is technically simple:
However, R is not returning any F and P values – only Df, Sum Sq and
Mean Sq. I have to remove either Year or Pop in order to get the test
statistics. Why is this?
Thank you in advance!
Johan A. Stenberg, Umea University, Sweden
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