Re: Centering GSN color bar

From: Mary Haley <haley_at_nyahnyahspammersnyahnyah>
Date: Fri May 06 2011 - 21:29:19 MDT

Hi Chad,

This is really useful! This example inspired me to create a new
examples page on how to set contour levels for use with symmetric
color tables, and I added your example to this. I modified it to use
the BlRe colormap, since I already had two examples using the BlueRed
color map.

Thanks for contributing! If anybody else has an example to contribute
to this page (or any other page for that matter), we love to hear from


On Apr 18, 2011, at 12:28 AM, Chad Herman wrote:

> I've often plotted grids where a large majority of the data was
> positive and the rest negative. To get the colormap to give the
> correct impression of the data, I would set the color bar to be
> symmetric so blue would be interpreted as cold or cooling and red as
> warm or warming. Sometimes the ratio of warm/cold was so large that
> the color bar extents were too large and suppressed a great deal of
> detail.
> I've figured out how to calculate the proper values of
> gsnSpreadColorStart and gsnSpreadColorEnd to ensure that negative
> values will be blue and positive values will be red. Attached is a
> demonstration of the gsnColorRange function. You can tweek the
> plotting limits to see how well the code correctly calculates the
> gsnColorStart/End values. Note that if the color bar spacing is
> larger than the value where you want blue to transition to red, the
> transition will not occur at the intended value because it's too
> small to resolve.
> Chad
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Received on Fri May 6 21:29:35 2011

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