[R] bigglm binomial negative fitted value

[Thomas Lumley]

On Fri, Jun 1, 2012 at 1:17 AM, Yue Guan <pipehappy at gmail.com> wrote:
> Hi, there
>
> Since glm cannot handle factors very well. I try to use bigglm like this:
>
> logit_model <- bigglm(responser~var1+var2+var3, data, chunksize=1000,
> family=binomial(), weights=~trial, sandwich=FALSE)
>
> fitted <- predict(logit_model, data)
>
> only var2 is factor, var1 and var3 are numeric.
>
> I expect fitted should be a vector of value falls in (0,1)
>
> However, I get something like this:
> str(fitted)
>  num [1:260617, 1] -0.0564 -0.0564 -0.1817 -0.1842 -0.1852 ...
>  - attr(*, "dimnames")=List of 2
>  ..$ : chr [1:260617] "1" "2" "3" "4" ...
>  ..$ : NULL
>

As the help says, the default is predictions of the linear predictor.
To get predictions of the probability, use type="response"

   -thomas

-- 
Thomas Lumley
Professor of Biostatistics
University of Auckland