[ncl-talk] Strange Vector plotting behavior

[Barry Lynn]

Hi Rashed:

That's true, but the vector scheme is supposed to "know" that the data is
subsetted across the domain, and plot it accordingly (from start to end).

Barry

On Sat, May 30, 2020 at 10:12 PM Rashed Mahmood <rashidcomsis at gmail.com>
wrote:

> Hi Barry:
> When you do something like (::4) that means you are only keeping every
> fourth data point, in other-words you are sub-setting the data before
> plotting it.
>
> Cheers,
> Rashed
>
> On Sat, May 30, 2020 at 11:44 AM Barry Lynn <barry.h.lynn at gmail.com>
> wrote:
>
>> Hi Rashed:
>>
>> Thank you for your suggestion.  It's actually being plotted with the gsn
>> routines, and I was able to thin the vectors with a value of vcMinDistanceF
>> = 0.01.
>>
>> It remains a mystery why using the suggested approach (e.g., ::4) just
>> plots some of the data (hard to tell if it actually all the remaining data)
>> 1/4 of the way through the domain.
>>
>> It might have something to do with the fact that I zoomed the data
>> (subsetted it), while the vector routine is not aware of this (smaller
>> domain), but then why would it work just fine when all the data is plotted?
>>
>> Strange!
>>
>> Barry
>>
>> On Fri, May 29, 2020 at 7:58 PM Rashed Mahmood <rashidcomsis at gmail.com>
>> wrote:
>>
>>> Hi Barry,
>>> I have not used WRF routines so I am not sure if the following would
>>> work, however, if you want to thin your vectors it is better to use the
>>> resource " *vcMinDistanceF*", you might need to play with it a bit to
>>> get the desired look.
>>> See description here:
>>> https://www.ncl.ucar.edu/Document/Graphics/Resources/vc.shtml
>>>
>>> Cheers,
>>> Rashed
>>>
>>>
>>>
>>>
>>> On Thu, May 28, 2020 at 5:30 AM Barry Lynn via ncl-talk <
>>> ncl-talk at ucar.edu> wrote:
>>>
>>>> Hello:
>>>>
>>>> I left out the text.
>>>>
>>>> Before copying it, I have to mention that the cross-section is an
>>>> excerpt from the entire domain. But, radar, etc, and temperature (not
>>>> shown) contour correctly.  That is, temperature maps correctly.
>>>>
>>>> The excerpted winds seem to be mapping to just 1/4 of the domain.
>>>>
>>>> Hello:
>>>>
>>>> I am making vertical cross-sections.
>>>>
>>>> I wanted to map vectors onto the map, but when I thin the data to plot
>>>> fewer vectors I  end up with the vectors going 1/4 of the way across,
>>>> rather than just getting a thinner plotting of the vector data.
>>>>
>>>> The full vector plotting is without the "::4."  WIth the ::4, I get
>>>> just 1/4 of the cross-section covered.
>>>>
>>>> These lines cause the problem.
>>>>
>>>>         plot_a   = gsn_vector(wks,u_plane_a
>>>> (0:zmax_pos,::4),v_plane_a(0:zmax_pos,::4),vecres)
>>>>
>>>>         plot_b   =
>>>> gsn_vector(wks,u_plane_b(0:zmax_pos,::4),v_plane_b(0:zmax_pos,::4),vecres)
>>>>
>>>>         plot_c   =
>>>> gsn_vector(wks,u_plane_c(0:zmax_pos,::4),v_plane_c(0:zmax_pos,::4),vecres)
>>>>
>>>>
>>>> I have attached the code.  I am not sure why this doesn't work, since
>>>> it generally works as advertised.  One comment: I am subsetting the u,v
>>>> data before plotting it.
>>>>
>>>>
>>>> Code attached.  Sorry it's so long!
>>>>
>>>> On Thu, May 28, 2020 at 2:00 PM Barry Lynn <barry.h.lynn at gmail.com>
>>>> wrote:
>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Barry H. Lynn, Ph.D
>>>>> Senior Associate Scientist, Lecturer,
>>>>> The Institute of the Earth Science,
>>>>> The Hebrew University of Jerusalem,
>>>>> Givat Ram, Jerusalem 91904, Israel
>>>>> Tel: 972 547 231 170
>>>>> Fax: (972)-25662581
>>>>>
>>>>> C.E.O, Weather It Is, LTD
>>>>> Weather and Climate Focus
>>>>> http://weather-it-is.com
>>>>> Jerusalem, Israel
>>>>> Local: 02 930 9525
>>>>> Cell: 054 7 231 170
>>>>> Int-IS: x972 2 930 9525
>>>>>
>>>>>
>>>>
>>>> --
>>>> Barry H. Lynn, Ph.D
>>>> Senior Associate Scientist, Lecturer,
>>>> The Institute of the Earth Science,
>>>> The Hebrew University of Jerusalem,
>>>> Givat Ram, Jerusalem 91904, Israel
>>>> Tel: 972 547 231 170
>>>> Fax: (972)-25662581
>>>>
>>>> C.E.O, Weather It Is, LTD
>>>> Weather and Climate Focus
>>>> http://weather-it-is.com
>>>> Jerusalem, Israel
>>>> Local: 02 930 9525
>>>> Cell: 054 7 231 170
>>>> Int-IS: x972 2 930 9525
>>>>
>>>> _______________________________________________
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>>>
>>>
>>
>> --
>> Barry H. Lynn, Ph.D
>> Senior Associate Scientist, Lecturer,
>> The Institute of the Earth Science,
>> The Hebrew University of Jerusalem,
>> Givat Ram, Jerusalem 91904, Israel
>> Tel: 972 547 231 170
>> Fax: (972)-25662581
>>
>> C.E.O, Weather It Is, LTD
>> Weather and Climate Focus
>> http://weather-it-is.com
>> Jerusalem, Israel
>> Local: 02 930 9525
>> Cell: 054 7 231 170
>> Int-IS: x972 2 930 9525
>>
>>

-- 
Barry H. Lynn, Ph.D
Senior Associate Scientist, Lecturer,
The Institute of the Earth Science,
The Hebrew University of Jerusalem,
Givat Ram, Jerusalem 91904, Israel
Tel: 972 547 231 170
Fax: (972)-25662581

C.E.O, Weather It Is, LTD
Weather and Climate Focus
http://weather-it-is.com
Jerusalem, Israel
Local: 02 930 9525
Cell: 054 7 231 170
Int-IS: x972 2 930 9525
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