[R] Almost a GAM?

[Michael Roberts]

Hello:

I sent this question the other day with the wrong subject
heading and couple typos, with no response.  So, 
here I go again, having made those corrections.

I would like to estimate, for lack of a better description,
a partially additive non-parametric model with the following
structure:

z~ f(x,y):w1 + g(x,y):w2 + e

In other words, I'd like to estimate the marginals with 
respect to w1 and w2 as nonparametric functions of 
x and y.    

I'm not positive, but I think I recall being able to estimate
a model like this using Splus gam function a couple years
ago (I no longer have Splus).  Although, I can
see that this would be a bit more difficult to do than a standard
gam with univariate partials and no interaction terms. The mgcv
gam function doesn't seem to like a function of this form.

Is there an R package that can estimate a model like this that
someone can point me toward?

Many thanks


Michael J. Roberts

Resource Economics Division
Production, Management, and Technology
USDA-ERS
(202) 694-5557 (phone)
(202) 694-5775 (fax)
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