[R] Discrete values in levelplot?
David Winsemius
dwinsemius at comcast.net
Sat Mar 27 16:04:07 CET 2010
On Mar 26, 2010, at 11:08 AM, Filipe Cadete wrote:
> Dear all,
>
> I am trying represent a matrix of discrete values. At the moment I
> am using levelplot from the lattice package, but it seems to only
> work with numerical values. Is there an option in levelplot that
> will allow me to assign a color to a discrete value, or another
> package that will do the same?
>
> To clarify, with levelplot I can represent a matrix such as:
> [,1] [,2] [,3] [,4]
> [1,] "1" "1" "1" "1"
> [2,] "1" "5" "5" "2"
> [3,] "1" "3" "3" "3"
>
> Which when plotted will have colors assigned based on a continuous
> scale of values (from 1 to 5 in this case).
>
> What I am looking for is a way to represent a matrix of the type:
>
> [,1] [,2] [,3] [,4]
> [1,] "A" "B" "C" "D"
> [2,] "A" "E" "D" "A"
> [3,] "B" "C" "C" "C"
>
> where each letter would have a specific color assigned to it.
This would be one way to convert letters to R color names:
cmtx <-matrix(sample(LETTERS[1:8], 25, TRUE), ncol=5)
Vswitch <-Vectorize(switch)
Vswitch(EXPR=cmtx, A="red", B="yellow", C="orange", D="brown",
E="blue", F="green", G="pink", H="light red")
But that did not provide a clear path to success with either
levelplot() or image():
> image(1:5, 1:5, matrix(Vswitch(EXPR=cmtx, A=1, B=2, C=3, D=4, E=5,
F=6, G=7, H=8), ncol=5) )
# worked
> cmtx
[,1] [,2] [,3] [,4] [,5]
[1,] "E" "H" "C" "F" "G"
[2,] "D" "F" "H" "B" "F"
[3,] "B" "B" "G" "C" "H"
[4,] "H" "H" "B" "D" "C"
[5,] "E" "F" "G" "A" "B"
> ??ascii
> require(R.oo); charToInt(cmtx)
Loading required package: R.oo
Loading required package: R.methodsS3
R.methodsS3 v1.0.3 (2008-07-02) successfully loaded. See ?R.methodsS3
for help.
R.oo v1.6.5 (2009-10-30) successfully loaded. See ?R.oo for help.
[1] 69 68 66 72 69 72 70 66 72 70 67 72 71 66 71 70 66 67 68 65 71
70 72 67 66
# wrong "scale" for colors in R
> charToInt(cmtx)-charToInt("A") +1 # avoid "zero colors"
[1] 5 4 2 8 5 8 6 2 8 6 3 8 7 2 7 6 2 3 4 1 7 6 8 3 2
> image(matrix(charToInt(cmtx)-charToInt("A") +1, ncol=5) )
Same result as above.
--
David Winsemius, MD
West Hartford, CT
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