[R] predict.glm

David Winsemius
Sat, 16 Jan 2010 20:35:27 -0000

On Jan 16, 2010, at 1:34 PM, Maurice Charbit wrote:

> Hi,
>
> See below I reply your message for
<https://stat.ethz.ch/pipermail/r-help/2008-April/160966.html
> >[R] predict.glm & newdata posted on Fri Apr 4 21:02:24 CEST 2008
>
>
> You say  it ##works fine but it does not: if you look at the length
> of yhat2, you will find 100 and not 200 as expected. In fact
> predict(reg1, data=x2) gives the same results as predict(reg1).
>
>
> So I am still looking for a solution of this problem.

You are replying to a posting that is almost two years old. The
posting back then was incomplete in that y1 was never defined. Why not
post a more complete and updated question?

--
David.
>
>
> best regards
>
> Maurice
>
> ==========>
> Hi,
>
> could it be the "newdata" argument? When I run predict with the
> newdata
> argument, I get an error message - a different one though. The
> second reason
> might be that your dataset is named df, which is defined as a
> function an
> may produce problems. Try renaming the dataset.
>
> yhat=predict(reg1,newdata=x2)
>
> x1=seq(1:100)
> r.norm1=rnorm(100,0,20)
> x1=r.norm1+x1
>
> x2=x1*2
> r.norm2=rnorm(200,0,20)
> x2=r.norm2+x2
>
> reg1=glm(y1~x1,binomial)
> yhat=predict(reg1)                   ##prediction works fine
> yhat=predict(reg1,newdata=x2) ##gives error message because of
> "newdata"
>
>> Error in eval(predvars, data, env) :
>  numeric 'envir' arg not of length one
>
> yhat=predict(reg1,data=x2) ##works fine
>
> ##using offset
>
> ofst=rep(0.5,100)
>
> reg1=glm(y1~x1,binomial,offset=ofst)
> yhat=predict(reg1)
> yhat1=predict(reg1,newdata=x2) ##gives error message
> yhat2=predict(reg1,data=x2)      ##works fine
>
>
> % ================================================> % Maurice CHARBIT
> % Ecole Nationale Sup?rieure des T?l?communications
> % D?partement TSI
> % 37,39 rue Dareau, pi?ce A321
> % 75634 - PARIS cedex 13 FRANCE
> % email: maurice.charbit at telecom-paristech.fr
> % Fax:   (33) (0)1 45 81 71 44
> % Phone: (33) (0)1 45 81 71 78
> %==================================================|
> 	[[alternative HTML version deleted]]
>
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David Winsemius, MD
Heritage Laboratories
West Hartford, CT