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..

Color matrix

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.

Why don't you use image() function? See http://stackoverflow.com/questions/13310597/r-are-there-convenient-way-for-displaying-a-picture-from-a-matrix-other-than/13311266#13311266 — Ali, Nov 16 '12 at 15:49
Is it homework (there's a tag for homework)? Does it need to be lattice? For both base graphics and ggplot solutions come to my mind immediately... — cbeleites unhappy with SX, Nov 17 '12 at 12:09

cbeleites unhappy with SX · Answer 1 · 2012-11-17T12:28:28.170

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.

edited Nov 17 '12 at 12:28

answered Nov 17 '12 at 12:17

cbeleites unhappy with SX

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score 0 · Answer 2 · answered Nov 16 '12 at 22:23

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) )

can i change the color of a random cell with this approach? i mean i want to change the color of [3,3] — trood, Nov 17 '12 at 07:02

Color cells of a matrix with RGB

2 Answers2