Color cells of a matrix with RGB

Question

Is it possible to draw a color matrix using levelplot function in the R package lattice? I must color each cell with an RGB function.

The color matrix must be like below and i need to color each cell like rgb(1,0.8,0.9) etc..

I need this because i have to implement self-organizing-map algorithm for color classification. i am not allowed to use built-in kohonen/som functions or som classes.

Answer 1

Have look at Murrel: (2011) Raster Images in R Graphics

It gives an excellent explanation how to do such things in base R or in grid.

Answer 2

This shows you how the rgb colors are encoded in the result from rainbow() and how levelplot will handle that argument to col.regions:

str(  rainbow(100)) 
# chr [1:100] "#FF0000FF" "#FF0F00FF" "#FF1F00FF" "#FF2E00FF" "#FF3D00FF" ...

The red, green and blue arguments range across 0 to FF and the transparency value is FF, so this produces a single band across the range of values:

levelplot(matrix(1:100, 100), region=TRUE, col.regions=rainbow(100) )

And this gives you a (horrible) color matrix:

levelplot(matrix(1:10000, 100), region=TRUE, col.regions=rainbow(100) )