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warning message in a glm model
2 messages · Alfonso Pérez, (Ted Harding)
On 21-Mar-08 15:59:05, Alfonso P?rez wrote:
Hello, my name is Alfonso. I want to apply a logistic model to my data.
The variables are, fish length and age length as a continous variable,
and cohort as a factor. I consider the interaction between age and
cohort in the model. The dependent variable is the probability of being
mature. Then the model is as follow:
ogive <- glm(mature~length+(cohort*age), family=binomial,
data=subset.cod)
But when I run it in R I obtain a Warning message:
Warning message:
In glm.fit(x = X, y = Y, weights = weights, start = start, etastart =
etastart, :
fitted probabilities numerically 0 or 1 occurred
I don't understand what's the problem, could you help me? thank you
in advance.
Alfonso.
There was effectively the same question from Werner Wernersen: "[R] glm.fit: "fitted probabilities numerically 0 or 1 occurr" 11 March 2008 08:58:55. See my response to him: "Re: [R] glm.fit: "fitted probabilities numerically 0 or 1 occurr" From: (Ted Harding) <Ted.Harding at manchester.ac.uk> Date: Tue, 11 Mar 2008 10:08:09 -0000 (GMT) which covers the maun issues. The underlying reason is that some linear function of your covariates compeletly separates the "Y=1" cases from the "Y=0" cases, so the GLM can predict probability 1 for "Y=1", and probability 0 for "Y=0". Best wishes, Ted. -------------------------------------------------------------------- E-Mail: (Ted Harding) <Ted.Harding at manchester.ac.uk> Fax-to-email: +44 (0)870 094 0861 Date: 21-Mar-08 Time: 16:53:54 ------------------------------ XFMail ------------------------------