Hi,
(PS This was originally posted to r-help, but didn't get a reply, so
am trying again here)
I am trying to fit a smoothing model where there are three dimensions
over which I can smooth (x,y,z). I expect interactions between some,
or all, of these terms, and so I have set up my model as
mdl <- gam(PA ~ s(x) + s(y) + s(z) + te(x,y) + te(x,z) + te(y,z) +
te(x,y,z),...)
I have recently read about the ti(), "tensor product interaction
smoother", which takes care of these interaction terms elegantly and
does the nesting properly.