[ncl-talk] Overlaying two plots onto the same contour map

[Rick Brownrigg]

I might also speculate that you have not associated the lon/lat arrays as
"coordinate variables" to the variable "data", as  i) that doesn't happen
automatically with ascii data, and ii) that process is not illustrated in
example overlay_12.ncl. When you obtain a plot of one or both plots
separately, do the tick mark labellings look like reasonable geographical
coordinates? Or grid coordinates perhaps?

Check out the following link and search for *Attaching coordinate arrays to
a variable*
There you'll find several examples of how to assign coordinates to your
data.

    http://ncl.ucar.edu/Applications/concepts_list.shtml

Rick


On Wed, Nov 20, 2019 at 7:09 AM Rashed Mahmood via ncl-talk <
ncl-talk at ucar.edu> wrote:

> Hi Giulio,
> The following should NOT work in your example (since you are not plotting
> a map plot here):
>    tb_plot = gsn_csm_contour_map(wks,tb,tres)
>
> It should be " tb_plot = gsn_csm_contour(wks,tb,tres)"
>
> I do not know if there are other issues, if there are please provide full
> script and a picture and may be the data file.
>
> Cheers,
> Rashed
>
>
>
>
>
>
> On Wed, Nov 20, 2019 at 11:49 AM G.Monte--- via ncl-talk <
> ncl-talk at ucar.edu> wrote:
>
>> Dears all,
>> I have some problems in overlaying two plots onto the same contour map.
>> The data fields to be overlayed are arranged into an ascii file and are
>> read in the following way by NCL 6.4.0:
>> ;---read longitude
>> lon  = dataf(:,4)
>>
>> ;---read latitude
>> lat  = dataf(:,3)
>>
>> ;---read tb
>> tb   = dataf(:,6)
>>
>> ;---read data
>> flag = dataf(:,11)
>>
>> For plotting them, I follwed the template shown in overlay_12.ncl, where I
>> set:
>> ;---Create the two plots
>>   tb_plot = gsn_csm_contour_map(wks,tb,tres)
>>   vv_plot = gsn_csm_contour(wks,flag,dres)
>> ;---Overlay the vv plot on the tb plot
>>   overlay(tb_plot,vv_plot)
>> ;---Drawing the tb plot will also draw vv plot
>>   draw(tb_plot)
>>   frame(wks)
>>
>> By doing so, only the second data field (named "flag") appeared in the
>> plot, while the first field (named "tb") did not; it appears only if I
>> plot them separately.
>> I really don't understand the reason, I kindly ask you a suggestion.
>>
>> Thank you,
>> Giulio
>>
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