[ncl-talk] Adding arrow head at the and of the polylines

[Xi Chang]

Thanks, Adam and Mary!

Yes, Adam, that's exactly what I need. I need to point the general
direction of the atmospheric circulation in my lat-height plot.

Thanks a lot,

Cheers,
Chang.



On Mon, Jun 19, 2017 at 12:42 PM, Adam Phillips <asphilli at ucar.edu> wrote:

> Hi Chang,
> As Mary noted this is a user-donated function and thus is not officially
> supported by the NCL project. However, I was able to get an arrow drawn on
> the first example of the latitude x height applications page by using the
> donated arrow function here:
> http://www.ncl.ucar.edu/Applications/height_lat.shtml#ex1
>
> I have attached the modified version of h_lat_1.ncl along with the
> resulting graphic. Note that you can pass gs resources into the arrow
> function to modify the color, thickness, etc as is shown on the polyline
> applications page here:
> http://www.ncl.ucar.edu/Applications/polyg.shtml
>
> Hope that helps. If you have any further questions please respond to the
> ncl-talk email list.
> Adam
>
>
>
>
> On Mon, Jun 19, 2017 at 11:33 AM, Mary Haley <haley at ucar.edu> wrote:
>
>> Chang,
>>
>> This is a user-donated function that I am unfamiliar with.
>>
>> The code seems straight-forward enough.  If the head is simply at the
>> wrong end of the vector, then you should be able to change arrow.ncl to
>> swap which end the head is considered to be.
>>
>> If you are trying to create a pressure/latitutde plot with vectors, then
>> you may want to look into gsn_csm_pres_hgt_vector. This requires that you
>> have a 2D array of U and V values which you will need to seed with your own
>> values:
>>
>> http://www.ncl.ucar.edu/Document/Graphics/Interfaces/gsn_
>> csm_pres_hgt_vector.shtml
>>
>> --Mary
>>
>>
>> On Mon, Jun 19, 2017 at 10:19 AM, Xi Chang <xi.chang01 at gmail.com> wrote:
>>
>>> Hi Mary and NCL,
>>>
>>> The script for the arrow-head can only work in the X and Y are in
>>> cartesian coordinate. It did NOT work when *X is the latitude and Y is
>>> the height* (hPa), the head of the vector is placed wrongly when I used
>>> "polylines" function. Can you help me with this issue?
>>>
>>> Best,
>>>
>>> Chang
>>>
>>>
>>>
>>>
>>>
>>> On Thu, May 11, 2017 at 3:42 PM, Mary Haley <haley at ucar.edu> wrote:
>>>
>>>> Xi,
>>>>
>>>> I don't think we have any examples of this, but I typed "arrow
>>>> polyline" in the search box of the NCL home page, and found this post by
>>>> Arindam Chakraborty:
>>>>
>>>> https://www.ncl.ucar.edu/Support/talk_archives/2010/1344.html
>>>>
>>>> I've attached the arrow.ncl script that he included in that post. You
>>>> should be able to run it as-is.
>>>>
>>>> --Mary
>>>>
>>>>
>>>> On Wed, May 10, 2017 at 5:28 PM, Xi Chang <xi.chang01 at gmail.com> wrote:
>>>>
>>>>> Dear NCL,
>>>>>
>>>>> Is there any a function to add an arrow head to show the direction of
>>>>> a line (using polylines)?
>>>>> Thanks a lot,
>>>>>
>>>>> Best,
>>>>> Xi
>>>>>
>>>>> _______________________________________________
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>>>>
>>>
>>
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>
>
> --
> Adam Phillips
> Associate Scientist,  Climate and Global Dynamics Laboratory, NCAR
> www.cgd.ucar.edu/staff/asphilli/   303-497-1726 <(303)%20497-1726>
>
> <http://www.cgd.ucar.edu/staff/asphilli>
>
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