[ncl-talk] Missing color fill with fixed contour levels

[Rick Brownrigg]

Hi Dave,

I get the same blank map running your script using 6.3.0 on yellowstone.
However, running your script unmodified using a current development
snapshot of the code, I get a correctly filled, mono-colored map
(attached).  So the issue appears to have cropped up before and has been
fixed -- I don't know the details.

Do you need a binary of the development branch -- its usually quite stable?

Rick


On Wed, Dec 30, 2015 at 6:25 PM, Dave Allured - NOAA Affiliate <
dave.allured at noaa.gov> wrote:

> NCL team,
>
> I am making ordinary color filled contour maps of gridded data, with fixed
> contour levels.  When all data values lie between two adjacent contour
> levels, all one color is expected.  However, NCL 6.3.0 fails to color fill
> in these cases.  The result is all white maps that interrupt presentation
> sequences.
>
> Attached plot #1 shows color fill forced by adding an intermediate contour
> level.  Plot #2 shows the problem, a blank plot when fewer contour levels
> are selected, and all one color expected.
>
> Here is the script for plot #2, the non-filled map.  Plot #1 results by
> changing cnLevelSpacingF to 6 instead of 12.  The input file is in the
> third attachment:
>
> begin
>   f = addfile ("data.no-color.nc", "r")
>   dat = f->dat
>   print ("Data range of full grid = " + min (dat) + ", " + max (dat))
>
>   wks = gsn_open_wks ("x11", "plot.test")
>   res                      = True
>   res at cnFillOn             = True
>   res at cnConstFEnableFill   = True
>
>   res at cnLevelSelectionMode = "ManualLevels"
>   res at cnMinLevelValF       = 0
>   res at cnMaxLevelValF       = 24
>   res at cnLevelSpacingF      = 12   ; smaller generates color fill
>
>   res at mpMinLonF    = 234     ; any boundary outside data limits
>   res at mpMaxLonF    = 260     ; generates color fill
>   res at mpMinLatF    = 31
>   res at mpMaxLatF    = 50
>
>   res at mpCenterLonF = (res at mpMinLonF + res at mpMaxLonF) / 2.0
>   res at gsnAddCyclic = False
>   res at mpFillOn     = False
>   res at mpOutlineBoundarySets = "AllBoundaries"
>
>   plot = gsn_csm_contour_map_ce (wks, dat, res)
> end
>
> Please note that two different kinds of changes result in correct color
> fill, just not all one color which is what I need.  You can decrease
> cnLevelSpacingF to some value such as 6, which generates more than one
> color.  You can also change any of the map border resources (mpMinLonF
> etc.) to extend outside the data limits, resulting in missing values along
> the edges showing as blank (white) areas.
>
> Both of these changes have something in common.  They all result in at
> least one color variation inside the plot frame.  The failure occurs when
> the entire plot frame should be one solid color with no breaks for missing
> values or contour lines.
>
> Is this a bug in NCL?  Is there an existing solution?  Can you please
> either change NCL to prevent this kind of blanking, or else add a resource
> similar to cnConstFEnableFill, to allow users to control the blanking in
> such cases?  Thanks for your consideration.
>
> --Dave
>
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