[R] negative predicted values in poisson glm

[Peter Dalgaard]

"P. Olsson" <olsson1 at 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.


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