You get the error because you have two unnested models with the same number of parameters, so the F numerator is divided by 0. (But this is merely a symptom of incorrect usage.)
On Tue, 22 Feb 2005, Jan Verbesselt wrote:
Dear R-list,
*When comparing two logistic regression models with the anova CHi test, I obtain the following error: (there are no NA's in the time series). How can this be solved such that I can compare two models on the same dataset were different explanatory variables are used?
l.KBDI <- glm(zna.arson2 ~ zna.KBDI,family = binomial) l.NDWI <- glm(zna.arson2 ~ zna.NDWI,family = binomial)
anova(l.KBDI,l.NDWI, test = "Chi")
Analysis of Deviance Table
Model 1: zna.arson2 ~ zna.KBDI Model 2: zna.arson2 ~ zna.NDWI Resid. Df Resid. Dev Df Deviance P(>|Chi|) 1 110 123.227 2 110 113.593 0 9.635 Warning message: NaNs produced in: pchisq(q, df, lower.tail, log.p)
*Is this caused by the non-linearity of the data? *How can I obtain a p-value?
-- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595
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