I hope it helps.
Best, Dimitris
p.s., you referred to `non-linearity of the data' if you mean that the probability of positive responses is a nonlinear function of your explanatory variables then you could use splines to model it (see e.g., at function `lrm()' from the Design package).
---- Dimitris Rizopoulos Ph.D. Student Biostatistical Centre School of Public Health Catholic University of Leuven
Address: Kapucijnenvoer 35, Leuven, Belgium Tel: +32/16/336899 Fax: +32/16/337015 Web: http://www.med.kuleuven.ac.be/biostat/ http://www.student.kuleuven.ac.be/~m0390867/dimitris.htm
----- Original Message ----- From: "Jan Verbesselt" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Tuesday, February 22, 2005 3:19 PM
Subject: [R] ERROR NaNs produced;when comparing two logistic regression models with the ANOVACHI test
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/
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