[R] R wont accept my zero count values in the GLM with quasi_poisson dsitribution

[John Maindonald]

A further point to note is that with a log link, SEs for comparisons with any factor
level where counts are all zero will be huge and meaningless.  This phenomenon
has the name Hauck-Donner effect, though more commonly so identified for
comparisons with categories with very low or very high estimated proportions
for binomial data.  For the poisson or quasipoisson family, use of the sqrt link
avoids this problem.


John Maindonald             email: john.maindonald at anu.edu.au<mailto:john.maindonald at anu.edu.au>


On 28/07/2015, at 22:00, r-help-request at r-project.org<mailto:r-help-request at r-project.org> wrote:

From: Andrew Robinson <A.Robinson at ms.unimelb.edu.au<mailto:A.Robinson at ms.unimelb.edu.au>>
Subject: Re: [R] R wont accept my zero count values in the GLM with quasi_poisson dsitribution
Date: 28 July 2015 18:59:51 NZST
To: Charlotte <charlotte.hurry at griffithuni.edu.au<mailto:charlotte.hurry at griffithuni.edu.au>>
Cc: "R help (r-help at r-project.org<mailto:r-help at r-project.org>)" <r-help at r-project.org<mailto:r-help at r-project.org>>


You have selected the binomial family in the call to glm.  You should
instead try something like

family=quasipoisson(link = "log")

I hope this helps

Andrew

On Tue, Jul 28, 2015 at 4:33 PM, Charlotte <
charlotte.hurry at griffithuni.edu.au<mailto:charlotte.hurry at griffithuni.edu.au>> wrote:

Hello

I have count values for abundance which follow a pattern of over-dispersal
with many zero values.  I have read a number of documents which suggest
that
I don't use data transforming methods but rather than I run the GLM with
the
quasi poisson distribution.  So I have written my script and R is telling
me
that Y should be more than 0.

Everything I read tells me to do it this way but I can't get R to agree.
Did I need to add something else to my script to get it to work and keep my
data untransformed? The script I wrote is as follows:

fit <- glm(abundance~Gender,data=teminfest,family=binomial())

then I get this error
Error in eval(expr, envir, enclos) : y values must be 0 <= y <= 1

I don't use R a lot so I am having trouble figuring out what to do next.

I would appreciate some help

Many Thanks
Charlotte






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--
Andrew Robinson
Deputy Director, CEBRA, School of Biosciences
Reader & Associate Professor in Applied Statistics  Tel: (+61) 0403 138 955
School of Mathematics and Statistics                        Fax: +61-3-8344
4599
University of Melbourne, VIC 3010 Australia
Email: a.robinson at ms.unimelb.edu.au<mailto:a.robinson at ms.unimelb.edu.au>
Website: http://www.ms.unimelb.edu.au/~andrewpr

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