Extrahieren von Farbinformationen aus ggplot2?

Question

Mit diesem Dummy-Code in einer Datei gespeichert namens foo.txt ...

COG,station1,station2,station3,station4,station5
COG000Z,0.019393497,0.183122497,0.089911227,0.283250444,0.074110521
COG0002,0.044632051,0.019118032,0.034625785,0.069892277,0.034073709
COG0001,0.033066112,0,0,0,0
COG0004,0.115086472,0.098805295,0.148167492,0.040019101,0.043982814
COG0005,0.064613057,0.03924007,0.105262559,0.076839235,0.031070155
COG0006,0.079920475,0.188586049,0.123607421,0.27101229,0.274806929
COG0007,0.051727492,0.066311584,0.080655401,0.027024185,0.059156417
COG0008,0.126254841,0.108478559,0.139106704,0.056430812,0.099823028

Ich habe eine Heatmap in ggplot2 mit dem beigefügten Code von nach dieser Antwort auf Stack .

> library(ggplot2)
> foo = read.table('foo.txt', header=T, sep=',')
> foomelt = melt(foo)
Using COG as id variables
> ggplot(foomelt, aes(x=COG, y=variable, fill=value)) + geom_tile() + scale_fill_gradient(low='white', high='steelblue')

Es erzeugt eine wirklich schöne Heatmap, aber ich bin wirklich nur nach den Farbcodes jeder Fliese (im Grunde des ursprünglichen foo aber mit Farbcodes anstelle der einzelnen Variablen). Jede Idee, wie über diese gehen?

Answer 1

Rather than extracting the colours from the plot, use colorRampPalette:

a<-colorRampPalette(c("white","steelblue"))
plot_colours<-a(n)

where n is the number of colours in your heat map. In your example, I get n=6 so:

n<-6
a(n)

returns

[1] "#FFFFFF" "#DAE6F0" "#B4CDE1" "#90B3D2" "#6A9BC3" "#4682B4"

and

image(1:n,1,as.matrix(1:n),col=a(n))

returns

Answer 2

I'm working on pulling all scale related code from ggplot2 into a separate package - this will make it much easier to use the same scales in different ways. See https://github.com/hadley/scales for the in progress code.