Colorful 3D Diagramm in r

Question

I am using persp to generate a 3D-diagram.

persp(MatrixY,ltheta = 120 ,theta = 30, phi = 30, expand = 0.19,,scale=FALSE,shade=0.4,border=NA,box=FALSE)

MatrixY has 128 rows and 416 columns which data are between -1 and +1. I want to color this diagram like this:

if values V between 0,5 and 1 then the line should be red, if values V between 0 and 0,5 then blue, if values V between -1 and 0 then green

How should I do this job?

Answer 1

Be aware that persp generates a plot of (nrows-1)*(ncols-1) cells, so the value of each colored cell represents the average of the 4 surrounding data points (see answer here). image() might give a better result, with one cell for each value in your matrix.

# generate a matrix
z = matrix(runif(n=100, min=-1, max=1),nrow=10,ncol=10)
nr <- nrow(z)
nc <- ncol(z)

# Calculate value at center of each cell ()
zfacet <- (z[-1, -1] + z[-1, -nc] + z[-nr, -1] + z[-nr, -nc])/4

# Generate the desired colors
cols = c('blue','green','red')

# Cut matrix values into 3 bins by manual breaks
zbinned <- cut(zfacet, breaks=c(-1,0,0.5,1))

# Plot perspective with colored cells
persp(z, ltheta = 120 ,theta = 30, phi = 30, expand = 0.19, asp=1, scale=T,shade=0.4, border=T, box=F, col=cols[zbinned])

There's your colorful 3d plot: