John Maindonald
2015-Jul-28 11:55 UTC
[R] R wont accept my zero count values in the GLM with quasi_poisson dsitribution
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 -- View this message in context: http://r.789695.n4.nabble.com/R-wont-accept-my-zero-count-values-in-the-GLM-with-quasi-poisson-dsitribution-tp4710462.html Sent from the R help mailing list archive at Nabble.com<http://nabble.com/>. ______________________________________________ R-help at r-project.org<mailto:R-help at r-project.org> mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html<http://www.r-project.org/posting-guide.html> and provide commented, minimal, self-contained, reproducible code. -- 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 MSME: http://www.crcpress.com/product/isbn/9781439858028 FAwR: http://www.ms.unimelb.edu.au/~andrewpr/FAwR/ SPuR: http://www.ms.unimelb.edu.au/spuRs/ [[alternative HTML version deleted]]