Re: Wavy contour lines in contour plot

From: Ekin Akoglu <ekin_at_nyahnyahspammersnyahnyah>
Date: Fri Feb 15 2013 - 06:35:24 MST

Dear Adam,

Thank you for your suggestions. I have tried using "cnSmoothing"
resources you have suggested but it did not give satisfactory
improvements. For a while, Mary and I exchanged a couple of
off-the-record mails on the issue and it seems that the issue boils
down to something related to the method used in regridding the data
before contouring. I will either try your second suggestion on using
smth9_Wrap function or try to plot the regridded data by MATLAB in NC
to justify whether it is a problem due to the regridding method used.
Actually, as you may remember, the MATLAB contour plot had smooth and
curvy contour lines whereas NCL did not. The problem with MATLAB was
it did not produce publication quality contour plot no matter how many
ways I tried. That's why I am trying to plot the data in NCL. Again
thank you for your suggestions.

Best regards,

Ekin

On Tue, Feb 12, 2013 at 10:25 PM, Adam Phillips <asphilli@ucar.edu> wrote:
> Hi Ekin,
> If you are asking about how to make the contours smoother, then you have
> two options:
>
> 1) Let NCL (semi-) automatically smooth the data:
> Set cnSmoothingOn = True
> http://www.ncl.ucar.edu/Document/Graphics/Resources/cn.shtml#cnSmoothingOn
> You may also need to set cnSmoothingTensionF and/or cnSmoothingDistanceF
> as is stated in the link above.
>
> 2) Smooth the data yourself:
> Before passing the data to gsn_csm_contour, you can smooth it yourself.
> I would recommend smth9_Wrap:
> http://www.ncl.ucar.edu/Document/Functions/Contributed/smth9_Wrap.shtml
>
> Good luck,
> Adam
>
>
> On 02/12/2013 01:16 PM, Mary Haley wrote:
>> Dear Ekin,
>>
>> I'm not sure what you mean by "curvy" lines versus "shaky" lines. Do you have
>> a plot sample from what you think the contours should look like?
>>
>> Are your coordinate axes correct? Do the data values in the contour
>> lines look correct?
>>
>> It would help if you could provide your data and your script.
>>
>> If you can provide your script and data, then see below for ftp information:
>>
>> http://www.ncl.ucar.edu/report_bug.shtml
>>
>> --Mary
>>
>> On Feb 12, 2013, at 1:00 AM, Ekin Akoglu wrote:
>>
>>> Dear all,
>>>
>>> I am plotting a contour graph from data and the contour lines which
>>> are drawn by NCL 6.0.0 looks wavy. I attached the plot to this e-mail.
>>> Do you have an idea about how to have curvy contour lines instead of
>>> these shaky drawn lines?
>>>
>>> Regards,
>>>
>>> Ekin Akoglu
>>>
>>> Institute of Marine Sciences
>>> Middle East Technical University
>>> P.O. Box 28, 33731
>>> Erdemli, Mersin
>>> Turkey
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> --
> ______________________________________________________________
> Adam Phillips asphilli@ucar.edu
> NCAR/Climate and Global Dynamics Division (303) 497-1726
> P.O. Box 3000
> Boulder, CO 80307-3000 http://www.cgd.ucar.edu/cas/asphilli
>
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-- 
Ekin Akoglu
Institute of Marine Sciences
Middle East Technical University
P.O. Box 28, 33731
Erdemli, Mersin
Turkey
Web: www.ims.metu.edu.tr
Email: ekin@ims.metu.edu.tr
Phone: +90 324 521 34 34
GSM: +90 506 554 03 90
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Received on Fri Feb 15 06:35:45 2013

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