[R] Plotting GAM fit using RGL

[Lucas Holland]

Hello all,

I’ve fitted a bivariate smoothing model (with GAM) to some data, using two explanatory variables, x and y.  Now I’d like to add the surface corresponding to my fit to a 3D scatterplot generated using plot3d(). 

My approach so far is to create a grid of x and y values and the corresponding predicted values and to try to use surface3d with that grid.

grid <- expand.grid(x = seq(-1,1,length=20),
                    y = seq(-1,1, length=20))

grid$z <- predict(fit.nonparametric, newdata=grid)

surface3d(grid$x, grid$y, matrix(grid$z, nrow=length(grid$x), ncol=length(grid$y)))

This however plots a number of surfaces that do not look like the fitted surface obtained by vis.gam(fit.nonparametric which actually looks a lot like the „truth“ (I’m using simulated data so I know the true regression surface). 

I think I’m using surface3d wrong but I can’t seem to spot my mistake. 

Thanks!