[Rd] question in value-based color in image()

[Uwe Ligges]

M. wrote:
> Hello,
> 
> I have a matrix with value varying from -1 to 1.  I hope to use scaled color
> based on its value to produce an image of this matrix.
> 
> Suppose I hope to label those data in [-1,-0.5] with blue, label those
> [-0.5,0.8] with light blue (tone is proportional to its value) and label
> those [0.8,1] with white.
> 
> How can I use image() and rgb() to achieve this?  It would be great if I can
> have a color scale legend, too.


1. This is a message for R-help (if at all), definitely not for R-devel!
2. Have you read ?image ?

Anyway, example:

image(matrix(c(-1, -0.6, -0.4, 1), ncol = 2),
       breaks = c(-1, -0.5, 0.8, 1),
       col = c("blue", "lightblue", "white"))

Uwe Ligges




> TIA,
> Chris
> 
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> 
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