Re: overlay contour (netto)

On Aug 9, 2013, at 1:01 PM, Xi Chang wrote:

> Hallo NCL,
>
> Thanks for the idea, However I just wonder
> 1. how can I possibly change the color, for instance from black to be *SlateBlue"? and

You will still have to use RGBA triplets in order to get the transparency, but first, you can see our list of named colors at:

http://www.ncl.ucar.edu/Document/Graphics/named_colors.shtml

Or the actual RGB values at:

http://www.ncl.ucar.edu/Applications/Scripts/rgb.txt

You'll see there's a color called "slate blue". You can then use the function "named2gba" to return the RGBA triplet for "slate blue".

I've updated the "newcolor_17.ncl" example to include this new function (which will be in V6.2.0) and the "slate blue" color.

http://www.ncl.ucar.edu/Applications/Scripts/newcolor_17.ncl

> 2. is it possible to overlay this netto contour with another contour line?

To overlay another contour line, you can use the same the same "overlay" procedure that's used in this example, except create a line contour plot instead of a filled plot:

;---Set some plot options
  lres = True

  lres@gsnDraw = False ; Don't draw plots or advance
  lres@gsnFrame = False ; frame (need to overlay later)

  lres@cnInfoLabelOn = False ; Turn off info label
  lres@cnLineColor = "limegreen" ; default is foreground (usually black)

  lres@cnLineThicknessF = 3.0
  lres@cnLineDrawOrder = "PostDraw"

   line_contour = gsn_csm_contour(wks,x,lres)
   overlay(ovly_plot1, line_contour)

>
> Thank you
>
>
> On Fri, Jul 26, 2013 at 1:15 AM, Mary Haley <haley@ucar.edu> wrote:
> Xi,
>
> See the attached example and image. Is this what you need? I draw the contour lines in different colors so you could see them in the final overlay plot.
>
> What I did was to set cnFillColors for both plots, using RGBA quadruplets. This allows me to set the transparency levels for each color.
>
> For the first plot, I made both contour fill colors (black and white) fully opaque (non-transparent).
>
> For the second plot, I made black fully opaque, and white fully transparent.This way, when you overlay, you will only see white if both contour areas are white in the same locations.
>
> --Mary
>
>
> On Jul 24, 2013, at 3:24 AM, Xi Chang wrote:
>
> >
> > Hallo NCL,
> >
> > I have a question, how can i possibly create such an overlay contour from two different fields, let's say:
> >
> > X (contour: negative value= black, positive value= white)
> > Y (contour: negative value= black, positive value= white)
> >
> > then do an "OVERLAY X slice Y". The result of overlay product from two contour map will be:
> >
> > if negative values + negative values == Black
> > if positive + negative == Black
> > if negative + positive == Black
> > if positive + positive === "WHITE"
> >
> > X slice Y.
> >
> > I really appreciate for your hints.
> >
> > Xi
> > _______________________________________________
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>
>
>

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Received on Fri Aug 9 20:04:21 2013