Hi,
Thanks for answering so quickly.
Actually, I do not have the John Fox's book. On this webpage, there is a
handout for logistic regression (GLM I'm interested in) (cf.
http://socserv.socsci.mcmaster.ca/jfox/Courses/SPIDA/logistic-regression-handout.pdf).
The summary function return standard errors for coefficient estimates but
not for predictions. According to
http://www.nag.co.uk/numeric/cl/Manual/pdf/G02/g02gbc.pdf<http://www.nag.co.uk/numeric/cl/Manual/pdf/G02/g02gbc.pdfprovides>
the standard errors for the linear predictors X \hat{\beta} is X C X^t where
C is the variance/covariance matrix of coefficient estimate \hat{\beta} .
But I do not know standard errors for a response.
Christophe
2008/8/27 <markleeds@verizon.net>
> Hi: you can check John Fox's CAR book if you have it. I don't
remember for
> sure but I may have standard error related calculations for some of
> his graphics in the GLM section of the book ? But, Can you not get the
> sigma^2 hat the summary of a GLM ? i would do
>
> glmsum<-summary("yourglmmodel") and check there.
>
> I'd be really surprised if the variance of the error term wasn't
there.
> Then, if you have that I think you can use that to calculate the prediction
> standard error as long as you assume that the parameters of the model are
> known with certainty. The formula for that is in the regular regression (
> non GLM ) textbooks but i don't remember it off the top of my head.
Good
> luck and hopefully someone else will reply with more exact info.
>
>
>
>
>
>
> On Wed, Aug 27, 2008 at 1:25 PM, christophe dutang wrote:
>
> Hi,
>>
>> I'm currently using biglm package to compute GLM outputs on a very
large
>> dataset. But no function computes standard erros of predictions. I look
in
>> what is done in R, namely in the function predict.glm.R in stats
package.
>> In this function, we call predict.lm to compute the standard errors
(line
>> 51). The code of predict.lm (in lm.R) is very hard to understand.
>>
>> I wonder if there is any good reference and / documentation on this
topic?
>> the manual at
>> http://www.nag.co.uk/numeric/cl/Manual/pdf/G02/g02gbc.pdfprovides
>> a good overview of the method used in R, but there is no reference
>> to standard errors...
>>
>> I suppose this topic have already raised in the past, but I found only
>> this
>> http://tolstoy.newcastle.edu.au/R/help/04/08/1762.html
>>
>> Thanks in advance
>>
>> Christophe
>>
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>>
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