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gnuplot and/or image[sc] questions

From: Josh Rigler
Subject: gnuplot and/or image[sc] questions
Date: Thu, 10 May 2001 12:38:22 -0600

I am attempting to plot a spectrogram.

My first question is how do I change my color map to a reasonable RGB
palette, rather than the 64 element grayscale default?  I've tried a
couple of different things, but I'm doing something wrong.  I would like
a palette that runs from about blue (weak signal) to red (strong

My second question is related.  I would like my frequency scale to be
log 10.  I don't think there is a reasonable way to do this with the
image[sc] routines.  I have the 3.8e version of gnuplot with pm3d
compiled in for 3-D surface plotting.  Using surfc.m then putting pm3d
in "map mode" works fairly well when my matrixes are relatively small,
but even a 128x400 (128 frequencies, 400 time steps) matrix seems to
overload gnuplot.  It plots about half the image, then just stops
plotting, while my gnuplot process runs away using 99.9% of my CPU!  Has
any one else tried this?  Can any one suggest a better method for
plotting spectrograms?


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