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MathGroup Archive 2001

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Two questions concerning ListDensityPlot ...

  • To: mathgroup at smc.vnet.net
  • Subject: [mg28497] Two questions concerning ListDensityPlot ...
  • From: Daniel Kattnig <d.kattnig at chello.at>
  • Date: Sun, 22 Apr 2001 21:03:15 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Dear Mathematica experts,

I'm actually trying to visualize sparsity patterns of matrixes using 
Mathematica's ListDensityPlot. However, doing so I have uncounted two 
problems ...

1. Given a (sparse) matrix A, I'm trying to establish a one-to-one 
correspondence between the plot and the matrix it is based on, i.e. I want 
the A[[1,1]] element to be plotted at the upper left and 
A[[Dimensions[A][[1]],Dimensions[A][[2]]]] at the lower right corner.  I've 
realized this by plotting Partition[Reverse@Flatten[A],Dimensions[A][[2]]] 
instead of A. However, doing so, I do not succeed in adjusting the labels 
appropriately since setting 
MeshRange->{{0,Dimensions[A][[1]]},{Dimensions[A][[2]],0}} does not invert 
the numbering of the ordinate as I've expected. Therefor my question is: 
How can I plot the matrix preserving the one-to-one correspondence and 
adjust the mesh such that the upper left corner corresponds to x=1, y=1 and 
the lower right to x=Dimensions[A][[2]], y=Dimensions[A][[1]]?

2. I'm desperately looking for a color function that allows the 
intermediate values to be kept white, while maxima and minima are colored 
red and blue respectively with the "color  intensity" indicating their 
absolute value. Applied to my sparse matrix problem I want the negative 
entries to be blue, the positive to be red whereas the majority of entries 
corresponding to zero should remain white. By the way, any suggestions 
concerning the visualization of complex valued entries are also highly 
appreciated. Is there an easy way to keep the phase information?

Sincerely,
Kattnig
two questions concerning ListDensityPlot



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