[R] ERROR NaNs produced; when comparing two logistic regression models with the ANOVA CHI test

[Jan Verbesselt]

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?


Thanks,
Jan

_______________________________________________________________________
ir. Jan Verbesselt 
Research Associate 
Lab of Geomatics and Forest Engineering K.U. Leuven
Vital Decosterstraat 102. B-3000 Leuven Belgium 
Tel:+32-16-329750   Fax: +32-16-329760
http://gloveg.kuleuven.ac.be/