[R] fitting a distribution using glm

[Peter Dalgaard]

"Vumani Dlamini" <dvumani at hotmail.com> writes:

> it is easy to fit a distribution using fitdistr
> 
> poisdata <- rpois(n = 100, lambda = 2)
> poismle <- fitdistr(poisdata, "Poisson")
> poismle
> 
> but i would like to know whether its possible to get an identical result 
> using glm. I use
> 
> poistab <- data.frame(table(poisdata))
> colnames(poistab) <- c("width","freq");
> poistab[,"width"] <- as.numeric(poistab[,"width"])
> glm(freq ~ 1-width, family = poisson, data = poistab)
> 
> but the results are always different.


Well, the freq values in that setup are not independent Poisson
variates. For a start, they sum to constant!

Try instead

exp(coef(glm(poisdata~1,family=poisson)))


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