[ncl-talk] White for zero in a map

[Alan Brammer]

Please read the two links below.  You have to define the coordinates of the
data, as detailed in the first link.  Then overlay the contours on the map,
can be done through the function in the 2nd link.

https://www.ncl.ucar.edu/Document/Graphics/overlays_on_map.shtml

https://www.ncl.ucar.edu/Document/Graphics/Interfaces/gsn_csm_contour_map.shtml

Good luck.



On Wed, Mar 4, 2015 at 12:41 PM, Jiang, Lifen <lfjiang at ou.edu> wrote:

>  Hi Dennis, Rick and Mary,
>
>  Sorry, I was using 6.0.0. I ran it aagin in 6.2.1 and got a figure like
> in "Plot_Diff". But I would like to see a figure like in "Map". Could you
> please give me more help?
>
>  Thank you for telling me my mistake.
>
>  Lifen
>
> ______________________________
>
>          *From:* Dennis Shea [shea at ucar.edu]
> *Sent:* Wednesday, March 04, 2015 10:48 AM
> *To:* Jiang, Lifen
> *Cc:* Mary Haley; ncl-talk at ucar.edu
>
> *Subject:* Re: [ncl-talk] White for zero in a map
>
>   What version of NCL are you using?
>
>
> https://www.ncl.ucar.edu/Document/Functions/Built-in/span_color_indexes.shtml
>
>  indicates that  this function is "
>
>
> *Available in version 6.2.0
> <https://www.ncl.ucar.edu/prev_releases.shtml#6.2.0> and later." *
>
> On Wed, Mar 4, 2015 at 9:38 AM, Jiang, Lifen <lfjiang at ou.edu> wrote:
>
>>  Hi Mary,
>>
>>  Thank you very much for writing the script for me! But it showed below
>> error when I ran it. I have attached the script and my data file again. It
>> will be helpful if you or anybody else can help tell the problem.
>>
>>  fatal:Undefined identifier: (span_color_indexes) is undefined, can't
>> continue
>>  fatal:Execute: Error occurred at or near line 23 in file diff_test.ncl
>>
>>  Thanks again,
>>
>>  Lifen
>>
>> ______________________________
>>
>>          *From:* Mary Haley [haley at ucar.edu]
>> *Sent:* Tuesday, March 03, 2015 3:29 PM
>> *To:* Jiang, Lifen
>> *Cc:* ncl-talk at ucar.edu
>> *Subject:* Re: [ncl-talk] White for zero in a map
>>
>>    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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>>>
>>
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