[R] Time trends with GAM

[Simon Wood]

For 1) see reply just sent to R help...
"Re: [R] Use pcls in "mgcv" package to achieve constrained cubic spline"
(I'm assuming you mean to fix the value of the smooth at a particular 
knot location - i.e. to impose a constraint like f(t_0) = b).

For 2) try 'model.matrix', or 'predict.gam' with argument 
'type="lpmatrix"' (see ?predict.gam)

On 23/03/13 01:05, Antonio P. Ramos wrote:
> Hi all,
>
> I am using GAM to model time trends in a logistic regression. Yet I would
> like to extract the the fitted spline from it to add it to another model,
> that cannot be fitted in GAM or GAMM.
>
> Thus I have 2 questions:
>
> 1) How can I fit a smoother over time so that I force one knot to be at a
> particular location while letting the model to find the other knots?

> 2) how can I extract the matrix from the fitted GAM so that I can use it in
> as an impute for a different model.
>
> The types of models I am running are to the following form:
>
> gam <- gam(mortality.under.2~ maternal_age_c+ I(maternal_age_c^2)+
> s(birth_year,by=wealth2) +
>               + wealth2 + sex +
>               residence+ maternal_educ + birth_order,
>             ,data=colombia2,family="binomial")
>
> I've read the extensive documentation for the GAM but I am not sure still.
> Any suggestion is really appreciated.
>
> Thanks,
>
> Antonio Pedro
>
> 	[[alternative HTML version deleted]]
>
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-- 
Simon Wood, Mathematical Science, University of Bath BA2 7AY UK
+44 (0)1225 386603               http://people.bath.ac.uk/sw283