Re: [R] negative predicted values in poisson glm

From: Peter Dalgaard <p.dalgaard_at_biostat.ku.dk>
Date: Thu 19 Jan 2006 - 02:52:33 EST

"P. Olsson" <olsson1@gmail.com> writes:

> Dear R helpers,
> running the following code of a glm model of the family poisson, gives
> predicted values < 0. Why?
>
> library(MASS)
> library(stats)
> library(mvtnorm)
> library(pscl)
> data(bioChemists)
> poisson_glm <- glm(art ~ fem + mar + kid5 + phd + ment, data = bioChemists,
> family = poisson)
> predicted.values = predict(poisson_glm)
> range(predicted.values)
>
>
> Thank you in advance for any hints.

The prediction is on the link scale.

-- 
   O__  ---- Peter Dalgaard             ุster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark          Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)                  FAX: (+45) 35327907

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Received on Thu Jan 19 03:52:15 2006

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