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Re: st: How to make prediction after a spline regression


From   Shige Song <sgsong@spymac.com>
To   <statalist@hsphsun2.harvard.edu>
Subject   Re: st: How to make prediction after a spline regression
Date   Tue, 13 Apr 2004 18:40:45 -0700

Dear Roger,

Thanks for the reply. One more thing, is the "noconstant" option in the logistic regression mandatory or optional? I did not include in my xtlogit model, it did not seem to influence the estimate (none of the spline terms was dropped). 

Shige

On Tue, 13 Apr 2004 12:16:54 +0100, Roger Newson wrote:
> At 11:34 09/04/04 -0700, Shige wrote:
>> Dear All,
>>
>>
>> I would like to follow my previous question about how to use
>> spline. Suppose I create a spline using "frencurv" and then
>> estimate a logistic regression like this:
>>
>> . frencurv, xvar(school) refpts(0(4)16) gen(sch) power(1) .
>> xtlogit unemp sch* X, re i(id) noconstant
>>
>> How to generated predicted probablity so that I can create a two-
>> way plot of "prob(unemp) by school", like the one in pp.7 in
>> bspline user guide? Thank you very much!
>>
>
> Figure 3 in the -bspline- user guide was created using -predict- as
> follows (under Stata 6):
>
> * frencurv with extended reference points (default) and cubic
> spline * frencurv,xvar(weight) refpts(1760(770)4840) gen(cs)
> power(3) describe cs* regress mpg cs*,noconst robust lincom cs3-cs5
> predict mpghat3
> grap mpg mpghat3 weight,s(o.) c(.L) xlab(1760(770)4840)
> ylab(0(5)45) t1(" ") l1("Mileage (mpg)") saving(fig3.gph,replace)
>
> Therefore, use -predict- after -xtlogit- to get predicted
> probabilities in the usual way.
>
> Roger
>
>
> --
> Roger Newson
> Lecturer in Medical Statistics
> Department of Public Health Sciences
> King's College London
> 5th Floor, Capital House
> 42 Weston Street
> London SE1 3QD
> United Kingdom
>
>
> Tel: 020 7848 6648 International +44 20 7848 6648
> Fax: 020 7848 6620 International +44 20 7848 6620
> or 020 7848 6605 International +44 20 7848 6605
> Email: roger.newson@kcl.ac.uk
> Website: http://www.kcl-phs.org.uk/rogernewson
>
>
> Opinions expressed are those of the author, not the institution.
>
>
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