[ncl-talk] color table issues

[Dennis Shea]

This question is not clear (to me).

To what  "color table exercises" are you referring?

Also, it is best to indicate what version of NCL you are using:

%> ncl -V

----
If you have a variable that spans (say)

  res at cnLevelSelectionMode = "ManualLevels"     ; set manual contour levels
  res at cnMinLevelValF       = -275.               ; set min contour level
  res at cnMaxLevelValF       =  350              ; set max contour level
  res at cnLevelSpacingF      =  25.               ; set contour spacing

there are (350-(-275))/25 = 25 contour levels

By default, NCL adds 2 more levels to 'catch' values less than -275 and
greater than 350. Hence, 27 (25+2) colors.

Say you are using the 256 color table:

  https://www.ncl.ucar.edu/Document/Graphics/ColorTables/amwg256.shtml

Then, by default, NCL will select every  27-th color so that

---
By default,

https://www.ncl.ucar.edu/Document/Graphics/Resources/cn.shtml#cnSpanFillPalette

   res at cnFillPallette = True

You can set this to False

   res at cnFillPallette = False      ; turn off spanning the color table

to select every color  but if you use the above settings you will get the
1st 27 colors in the 256-colr table.



 res at cnLevelSelectionMode = "ManualLevels"     ; set manual contour levels
  res at cnMinLevelValF       = -275.               ; set min contour level
  res at cnMaxLevelValF       =  350              ; set max contour level
  res at cnLevelSpacingF      =  2.5               ; set contour spacing


 350-(-275))/256 = 2.44



  res at cnLevelSpacingF      =  2.44               ; set contour spacing


Would use very color



On Wed, Sep 27, 2017 at 3:09 PM, Grace Choi <gracesh27 at gmail.com> wrote:

> Hello everyone,
>
> When I try on color table exercises on the ncl website, I only can get 31
> colors to show up on my x11, as opposed to 255 colors that the example
> shows. Should I be particularly concerned about this?
>
> Also, I am wondering if the issue above is related to the issue I've been
> having with other functions, such as gsn_define_colormap(wks,"rainbow").
> When I expect to see actual rainbow colors, I only see different shades of
> blue on my map. Please help.
>
> Sincerely,
> Grace
>
> _______________________________________________
> ncl-talk mailing list
> ncl-talk at ucar.edu
> List instructions, subscriber options, unsubscribe:
> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.ucar.edu/pipermail/ncl-talk/attachments/20170927/da78911b/attachment.html>