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color palette

3 messages · array chip, Thomas Lumley

Original
array chip
# 
Hi, I have a matrix with both positive and negative
numbers, I would like to use image() to draw a
heatmap. How can I can design a palette (or is there a
function already available) that treat negative
numbers in a blue gradient and positive numbers in a
red gradient and treat 0 as white?

Thanks
Thomas Lumley
#
On Wed, 3 Aug 2005, array chip wrote:

            

      
      
      
    

        
?colorRampPalette

 	-thomas

  
  


  


      

    

    

      
      

        


  

        

      array chip
    

    

      
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Thanks for the suggestion. I still could not figure
out how to use the function to do my job. What's
important in my job is that I have to map white color
to value 0, and then form a bue gradient for negative
values, and red gradient for positive values. The data
matrix I have is not symmetric aound 0, say 0 is at
the 18 percentile, and values range from -10 to 30.
How exactly I could do my job? Bear with me, I am new
to color, I don't quite understand how the image
function map the number is the data matrix to the
colors defined in the col argument.

Thanks

        
--- Thomas Lumley <tlumley at u.washington.edu> wrote: