[R] From THE R BOOK -> Warning: In eval(expr, envir, enclos) : non-integer #successes in a binomial glm!

[Rubén Roa]

-----Mensaje original-----
De: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] En nombre de Corrado
Enviado el: martes, 30 de marzo de 2010 16:52
Para: r-help at r-project.org
Asunto: [R] From THE R BOOK -> Warning: In eval(expr, envir, enclos) : non-integer #successes in a binomial glm!

Dear friends,

I am testing glm as at page 514/515 of THE R BOOK by M.Crawley, that is on proportion data.

I use glm(y~x1+,family=binomial)

y is a proportion in (0,1), and x is a real number.

I get the error:

In eval(expr, envir, enclos) : non-integer #successes in a binomial glm!

But that is exactly what was suggested in the book, where there is no mention of a similar warning. Where am I going wrong?

Here is the output:

 > glm(response.prepared~x,data=dddd,family=binomial)

Call:  glm(formula = response.prepared ~ x, family = binomial, data = dddd)

Coefficients:
(Intercept)            x 
    -0.3603       0.4480 

Degrees of Freedom: 510554 Total (i.e. Null);  510553 Residual
Null Deviance:      24420
Residual Deviance: 23240        AIC: 700700
Warning message:
In eval(expr, envir, enclos) : non-integer #successes in a binomial glm!
 >



Regards
-- 

Corrado Topi
PhD Researcher
Global Climate Change and Biodiversity
Area 18,Department of Biology
University of York, York, YO10 5YW, UK
Phone: + 44 (0) 1904 328645, E-mail: ct529 at york.ac.uk

---

Probably you are misreading Crawley's Book?
A proportion would usually be modeled with the Beta distribution, not the binomial, which is for counts.
If you are modeling a proportion try the betareg function in betareg package.
HTH
Ruben
 


____________________________________________________________________________________ 

Dr. Rubén Roa-Ureta
AZTI - Tecnalia / Marine Research Unit
Txatxarramendi Ugartea z/g
48395 Sukarrieta (Bizkaia)
SPAIN