Subject: [R] warnings associated with logistic regression
From: Allan Strand (stranda@cofc.edu)
Date: Wed 12 Jul 2000 - 02:20:37 EST
Message-ID: <86r990ocyy.fsf@linum.cofc.edu>
Hi all,
This is as much as statistical/estimation question as an R-specific
one, but here goes.
I am trying to use logistic regression to predict suitability of
habitats for certain plant species. The response variable is a binary
one that indicates whether a particular species is found at a site on
the landscape. The independent variables represent physical
characteristics of the landscape derived from a GIS. A significant
proportion of the time I get the following warning messages from
glm():
> lr <- glm(known.v1~elevation+aspect+slope+energy15+energy166+aspect+accum+streams.buffered,family=binomial,data=siteframe)
Warning messages:
1: Algorithm did not converge in: (if (is.empty.model(mt)) glm.fit.null else glm.fit)(x = X, y = Y,
2: fitted probabilities numerically 0 or 1 occurred in: (if (is.empty.model(mt)) glm.fit.null else glm.fit)(x = X, y = Y,
Now I can get the algorithm to converge (or at least not produce the
warning) by increasing the number of iterations, but that does not
affect the second warning. A read of Hosmer and Lemeshow (1989) does not
provide much insight, so I thought that I would post the question to
the list.
Any comments? Also, I'd be happy to email a dataset that exhibits this
behavior if anyone is curious enough.
Cheers,
A.
-- Allan Strand, Biology http://linum.cofc.edu College of Charleston Ph. (843) 953-8085 Charleston, SC 29424 Fax (843) 953-5453-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-help-request@stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._
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