On 10/21/2009 9:03 AM, Michael Ralph M. Abrigo wrote:
Hi all!
I am a grad stat student and is fairly new in using R. I am doing a
regression tree in one of my problem sets. I have already identified the
cut-points (using Stata) for the regression. My problem is how to graph the
fitted values of z against the independent variables x and y. Basically, I
want to graph the following:
z=87.67 if 0<x<=29 & 0<y<=48
z=75 if 0<x<=29 & 48<y<=62
z=67 if 29<x<=36 & 0<y<=62
z=56.71 if 36<x<=45 & 0<y<=62
z=40.8 if 36<x<=55 & 0<y<=62
I have some idea (still to be implemented) on how to graph them piece-wise
using "persp". My question is this:how do one combine multiple 3D graphs
(using "persp") in R? better yet, is there a way to graph them all in just
one go?
I would define a function of x and y which evaluates to your fitted
values, evaluate it on a grid, and then use persp. You might already
have code to do this, or you might have to write it something like this:
f <- function(x,y) {
ifelse( 0 < x & x <= 29 & 0 < y & y <= 48, 87.67,
ifelse( 0 < x & x <= 29 & y < 48 & y <= 62, 75,
}
etc. I leave the difficult problem of properly closing all the
parentheses to you!
Duncan Murdoch
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