[ncl-talk] White for zero in a map

[Mary Haley]

There are many ways you can do this.

I've attached a script that does this by using the cnFillColors resource to
specify a list of color indexes into the "rainbow" color map, but then I
changed the color index that represents level 0.0 to be 0 (the background
color, and therefore white).

--Mary


On Sun, Mar 1, 2015 at 3:01 PM, Jiang, Lifen <lfjiang at ou.edu> wrote:

>   Hello,
>
>  I was trying to create a map of the attached variable. The min and and
> max are -14 and 18, respectively.
>
>  I would like to set white for zero, but could not work out how to make
> it. Script is at the end of this email.
>
>  Could anybody help with my issue?
>
>  I appreciate your time and help!
>
>  Thanks,
>
>  Lifen
>
>  ;************************************************
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
>
> begin
>
>   in = addfile("Diff.nc","r")
>   t  = in->Diff
>   t at _FillValue  = -999
>   t at missing_value = t at _FillValue
>
>   printVarSummary(t)
>
>   wks = gsn_open_wks("png" ,"Plot_Diff")                ;
>   gsn_define_colormap(wks,"rainbow")        ; choose colormap
>
>   res                       = True     ; plot mods desired
>
>   res at cnFillOn              = True     ; turn on color fill
>   res at cnLinesOn             = False    ; turn off contour lines
>   res at cnLevelSpacingF       = 3      ; contour spacing
>
> ;---This resource not needed in NCL V6.1.0
>   res at gsnSpreadColors       = True     ; use full range of color map
>
>   res at lbLabelStride         = 1
>
>   res at pmTickMarkDisplayMode = "Always"; use NCL default lat/lon labels
>
>   res at gsnAddCyclic          = False    ; data already has cyclic point
>                                   ; this must also be set for any zoom
>
> ; note that the gsn_csm_*map_ce templates automatically set
> ; res at mpLimitMode="LatLon" for you. If you are plotting a different
> projection,
> ; you may have to set this resource.
>
>   res at mpMinLatF            = -90      ; range to zoom in on
>   res at mpMaxLatF            =  90
>   res at mpMinLonF            = -180
>   res at mpMaxLonF            = 180
>
>   res at cnLevelSelectionMode = "ManualLevels"
>   res at cnMinLevelValF       = -15
>   res at cnMaxLevelValF       = 20
>
>   plot = gsn_csm_contour_map_ce(wks,t({-90:90},{-180:180}), res)
>
>  end
>
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