[R] Comparing gam models fitted using ti()

[Arnaud Mosnier]

Dear R-Help list,

I want to compare gam models including interaction with simpler models.
For interaction models, I used gam(Y~ti(X1) + ti(X2) + ti(X1,X2))
removing the interaction, the models end as Y~ti(X1) + ti(X2)

How those models compare with models with the form Y ~ s(X1) + s(X2)

In my case, the former (i.e. ti() ) have a better AIC value than those with
s().

Should I keep the ti() form or use only the s() form when I have no
interaction ?

Thanks for your help !

Arnaud

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