[R] 3D Gaussian with different colors

[David Winsemius]

On Dec 25, 2012, at 11:58 PM, Roberto wrote:

> I wrote, finding pieces of code in the web, a simple script to draw  
> a 3D
> gaussian plot.

> For the next step, I need that the 2 gaussian distributions have  
> different
> colors.
>
> Can someone help me to do this?
>
> fn <- function(x, y, scale, scale2)
> dnorm(x,mean=1,sd=scale)*dnorm(y,mean=-1,sd=scale) +
> dnorm(x,mean=2,sd=scale2)*dnorm(y,mean=1,sd=scale2)
>
> x <- seq(-4,4,len=40)
> y <- seq(-4,4,len=40)
> z <- outer(x, y, fn, scale = 1, scale2 = 0.5)
> nrz <- nrow(z)
> ncz <- ncol(z)
> jet.colors <- colorRampPalette( c("lightblue", "green", "darkgreen") )
> nbcol <- 100
> color <- jet.colors(nbcol)
> zfacet <- z[-1, -1] + z[-1, -ncz] + z[-nrz, -1] + z[-nrz, -ncz]
> # Recode facet z-values into color indices
> facetcol <- cut(zfacet, nbcol)
> persp(x,y,z, theta = 30, phi = 30, expand = 0.2, col =  
> color[facetcol],
>      ltheta = 120, shade = 0.75, ticktype = "detailed")

There really is no specific division since both distributions  
contribute something at each point, so I took this to mean that you  
wanted something that might arise in an effort to divide the plane  
into two regions where their contributions were greatest. This effort  
was done by eyeball:

persp(x,y,z, theta = 30, phi = 30, expand = 0.2, col = c("blue", "red") 
[1+(row(z[-1,-1])+col(z[-1,-1]) <= 47)],
      ltheta = 120, shade = 0.75, ticktype = "detailed")


Need to construct an index matrix to the color vector that matches the  
dimensions of the facets which are one less than the dimensions of z  
(adding 1 since R indices need to start at 1 and logical FALSE is 0) .  
This constructs a matrix of conditions based on

David Winsemius, MD
Alameda, CA, USA