[ncl-talk] control legend values

[Adam Phillips]

Hi Sun,
Here's how I would do it:
gsn_define_colormap(wks,"ViBlGrWhYeOrRe”)
res = True
....
res at cnLevelSelectionMode = "ExplicitLevels"
res at cnLevels=(/-1000,-500,0,1000,5000,10000/) ; explicitly set contour
levels
res at cnFillOn = True
res at cnFillColors = (/12,27,0,0,63,75,95/)

Set the cnLevels to whatever you want, and then set the number of
cnFillColors to one more than the number of cnLevels. The integers that I
set in cnFillColors were chosen from the ViBlGrWhYeOrRe colormap website
here:
http://www.ncl.ucar.edu/Document/Graphics/ColorTables/ViBlGrWhYeOrRe.shtml

Color 12 is a blue, 27 is a blueish green, and so on. I set 0 (=background
color/white) for all areas greater than or equal to -500 and less than 0,
as well as all areas greater than or equal to 0 and less than 1000. (Note:
I could have specified color 52 instead of 0 as 52 also looks white.)

I don't know if you want to have -1000 and 10000 be the absolute minimum
and maximum values on your labelbar. If so, see labelbar example #14 here
(3rd panel):
http://www.ncl.ucar.edu/Applications/labelbar.shtml#ex14

Note that when you set lbLabelAlignment = "ExternalEdges" you will have to
set the lbLabelStrings resource as the example shows. If you go with
ExternalEdges some trial and error is likely needed to get the labelbar to
exactly where you want it to be.

Hope that helps. If you have further questions please respond to ncl-talk.
Adam






On Thu, Sep 8, 2016 at 12:03 PM, mireiyue <mireiyue at gmail.com> wrote:

> Dear NCL users,
>
> I want to create a legend that shows minimum -1000 and maximum 10000. I
> want to have different interval for negative and positive values. And I am
> using gsn_define_colormap(wks,"ViBlGrWhYeOrRe”) and I want to put white
> color for zero.
>
> I haven’t found any information about this work.
>
> I will appreciate any related helps and comments.
>
> Thank you
> Sun-
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-- 
Adam Phillips
Associate Scientist,  Climate and Global Dynamics Laboratory, NCAR
www.cgd.ucar.edu/staff/asphilli/   303-497-1726

<http://www.cgd.ucar.edu/staff/asphilli>
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