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. The help file says "This is much better than attempting the same thing with ?s?or ?te? terms representing the interactions (although mgcv does not forbid it)." There is a 2D example there also. But I don't understand how I should set this up for my 3D example. Does anyone have experience with this, and can explain how I should do it properly? Mark
mgcv: 3D tensor product smoothers and ti()
2 messages · Mark Payne, Ben Bolker
Mark Payne <markpayneatwork at ...> writes:
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.
[snip] to make gmane happy ... Appreciate that you would like help with this, but this is really very distantly (at best) related to mixed models ... is there perhaps an example in Simon Wood's book? Ben Bolker