Re: cnFill problem when all values are between levels

Hi Antti,
I have seen this problem as well. (Rick I believe that there is a JIRA
ticket on this issue about NCL not color filling a constant field.)
My work around has been to set a single grid point, usually near the
border of the plot, to a value outside the two levels..
If doing that doesn't work for you let ncl-talk know.. Adam

On 11/14/13 2:26 PM, antti.pessi@vaisala.com wrote:
>
> Hi Rick,
>
> Could you please try the script and see the values on the label bar.
> Those two sample values fall in to the second bin that should be blue.
>
> I tried something else to confirm: I get a white plot even if I change
> the colormap to e.g. "cosam" and put in values 4.1 and 4.9. If the two
> values are e.g. 3.9 and 4.1 the plot is fine. So every time the
> values fall inside two levels, the plot is white.
>
> Antti
>
> *From:*Rick Brownrigg [mailto:brownrig@ucar.edu]
> *Sent:* Thursday, November 14, 2013 1:48 PM
> *To:* Pessi Antti ANPE
> *Cc:* ncl-talk@ucar.edu
> *Subject:* Re: [ncl-talk] cnFill problem when all values are between
> levels
>
> Hi,
>
> With that particular colormap, I might expect the result to be a white
> plot. All your contour values fall into the first bin, and it seems
> like that first bin should be mapped to one of the first few colors of
> the colormap, all of which are white or very nearly white shades of
> blue (?)
>
> Rick
>
> On Nov 14, 2013, at 1:26 PM, antti.pessi@vaisala.com
> <mailto:antti.pessi@vaisala.com> wrote:
>
>
>
> Hello,
>
> I have seen this problem when all the values fall between two contour
> levels. The script doesn't give any error message, but doesn't plot
> anything either. For example, the script below (modified sample script
> conLev_5.ncl from NCL web site) should plot a blue field all over, but
> instead plots white field.
>
> Is this a bug or is there some resource or hack that I can use?
>
> Thanks,
>
> Antti
>
> ; ===========================================
> ; conLev_5.ncl
> ;
> ; Concepts illustrated:
> ; - Creating contours for a constant field
> ; - Explicitly setting contour levels
> ; - Explicitly setting the fill colors for contours
> ; - Centering labels with respect to labelbar boxes
> ; ===========================================
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
>
> ;----------------------------------------------------------------------
> ; Main code
> ;----------------------------------------------------------------------
> begin
> ;---Create a dummy array that will initially contain all missing values
> x = new((/33,33/),float)
>
> ;---Fill in values to make a square
>
> x(0:32,0:16) = 1.1
> x(0:32,17:32) = 1.2
>
> ;---Set all missing values to some non-missing value
> x = where(ismissing(x),50,x)
>
> wks = gsn_open_wks ("png", "conLev")
>
> res = True
> res@gsnMaximize = True
>
> res@cnFillOn = True
> res@cnLinesOn = False
> res@cnLineLabelsOn = False
> res@cnLineLabelBackgroundColor = -1
>
> cmap_rad = read_colormap_file("WhiteBlueGreenYellowRed")
> ; cmap_rad(0,3) = 0.0 ; Fully transparent
> res@cnFillPalette = cmap_rad
> res@cnLevelSelectionMode = "ExplicitLevels"
> res@cnLevels = ispan(1,5,1)
>
> plot = gsn_csm_contour(wks, x, res)
>
> end
>
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Received on Thu Nov 14 14:38:09 2013