On 21/11/2009 3:11 PM, Paul Simonin wrote:
Hello all,
Thank you for the previous assistance I received from this listserve!
My current question is: How can I create an appropriate matrix of
values from a GAM (actually a GAMM) to make a 3-D plot? This model is
fit as a tensor product spline of two predictors and I have used it to
make specific predictions by calling:
YoyRasPred6<-predict(YoyRas.Distribution.T.L.DT.gamm$gam,newdata=YoyRasSubset6,se.fit=T)
However, this type of command, I believe, produces only a vector of
values. I have plotted these values and know how to do so in 2-D.
However, I would like to create a 3-D plot, which I believe will require
an entire matrix of predictions (z values) based on all possible inputs
(x and y values). What is an efficient way to do this? It seems there
must be a better way than simply predicting vector after vector ... as I
am now, then piecing these together.
You can use expand.grid() to generate a dataframe corresponding to the
grid of values, then reshape the results into a matrix. I don't have
your data to show a fit, but this shows how the graphing is done.
> x <- 1:10
> y <- 1:12
> grid <- expand.grid(x=x, y=y) # give names to get named columns
> z <- matrix(apply(grid, 1, prod), nrow=10) # use predict instead here
> library(rgl)
> persp3d(x,y,z, col="red")
Duncan Murdoch
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