[R] glm deviance question

[Anne York]

I am comparing the Splus and R fits of a simple glm.    
In the following, foo is generated from rbinom with size = 20 p = 0.5.
The coefficients (and SE's0 of the fitted models are the same, but the
estimated deviances are quite different. Could someone please tell me why
they are so different? I am using R version 1.3.1 and Splus 2000 release 3
on windows 2000. 

++++++++++++++++++++++
foo <- c(9,  4, 10,  7, 11, 13,  8,  6, 11, 14, 11, 
         10,  7,  9, 13,  7,  9,  6, 10, 10)

foo.glm <- glm(cbind(foo,20-foo)~1,family=binomial)

In Splus: 

summary(foo.glm) 

Coefficients:
                Value Std. Error  t value 
(Intercept) 0.1502822  0.1002824 1.498589

(Dispersion Parameter for Binomial family taken to be 1 )

    Null Deviance: 21.89527 on 19 degrees of freedom

Residual Deviance: 21.89527 on 19 degrees of freedom


In R: 

summary(foo.glm)

Coefficients:
            Estimate Std. Error z value Pr(>|z|)
(Intercept)  -0.1503     0.1003  -1.499    0.134

(Dispersion parameter for binomial family taken to be 1)

    Null deviance: 26.479  on 19  degrees of freedom
Residual deviance: 26.479  on 19  degrees of freedom
AIC: 96.44


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Anne E. York
National Marine Mammal Laboratory
Seattle WA 98115-0070  USA
e-mail: anne.york at noaa.gov
Voice: +1 206-526-4039
Fax: +1 206-526-6615
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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