Re: Values inside a polygon

Hello,

Thanks again for the reply. The problem is not related to the plotting of
the variable. I put the plot there only to show that the polygon lies
within the lat/lon range of the grib file. My problem is that gc_inout does
not produce any 'True' value, meaning that the output suggests all points
lie outside of the polygon. Is there a particular direction
(clockwise/anti-clockwise) that the polygon indices need to be specified?

Note: In my script, the indices variable is used to count the 'True' values
produced by gc_inout. This variable consists of a missing value indicating
that only False values are produced by the function.

Manisha

On Tue, Jul 17, 2012 at 1:57 PM, Adam Phillips <asphilli@ucar.edu> wrote:

> Hi Manisha,
> (So you know: The reason I asked about the input/output
> latitudes/longitudes ranges matching is because ~90% of the time when
> people have issues with procedures/functions that have input/output
> lats/lons, it is due to a mismatch in range or direction of the
> coordinates.)
>
> Looking at your script, I think the issue is occurring because you are
> plotting T, and not T_new. If you change this:
> plot = gsn_contour_map(wks,T,res) ; Draw a contour plot.
> to this:
> plot = gsn_contour_map(wks,T_new,res) ; Draw a contour plot.
>
> your script works, and the resulting plot looks correct to me.
>
> In the future, we try to keep most ncl-talk communication online so that
> others can help in diagnosing issues. That way other ncl-talk subscribers
> can help out, and the original person who replied can get assistance from
> the community at-large in answering follow up issues. It's not a problem at
> all that you replied directly to me this time, but next time please respond
> to ncl-talk. Thanks! Adam
>
>
> On 07/16/2012 10:36 PM, Manisha Ganeshan wrote:
>
> Hi Adam,
>
> I am not sure what you mean by matching of the lat/lon range. I am
> certain that my polygon values lie within the specified lat/lon range in
> the grib file. Anyway, I have uploaded the grib file through ftp in the
> 'incoming' directory. I have renamed it as "gribfile.grb". I would be very
> grateful if you could kindly take a look, and figure out where I am going
> wrong.
>
> Thanks,
> Manisha
>
> On Mon, Jul 16, 2012 at 10:51 PM, Adam Phillips <asphilli@ucar.edu> wrote:
>
>> Hi Nisha,
>> I cannot see what is wrong with your script without the .grb file.
>> Generally, the first thing I would check is to make sure the polygon
>> latitudes/longitudes match the range of the latitudes/longitudes in the
>> .grb file. Thus, if the .grb file has longitudes that run from -180:180E,
>> your polygon coordinates should as well.
>>
>> If both the .grb file and your polygon ranges match, please follow the
>> directions here on how to send in your .grb file via ftp:
>> http://www.ncl.ucar.edu/report_bug.shtml
>> Adam
>>
>>
>> On 7/16/12 11:37 AM, Manisha Ganeshan wrote:
>>
>> Hi Adam,
>>
>> Thank you for your response. I tried using the gc_inout function in a
>> script to determine points lying inside a polygon. However, it appears to
>> produce false results. I am reading the polygon lat/lon values from a text
>> file, and am able to plot it successfully on a pre-defined map. However, I
>> cant seem to get the lat/lon values inside the polygon using gc_inout. The
>> function gives me "False" values for all points in my domain.
>>
>> I am attaching my script here, along with the auxiliary text files. Hope
>> that you can take a look and help me figure out what's going wrong.
>>
>> Thanks,
>> Nisha
>> On Fri, Jul 13, 2012 at 6:12 PM, Adam Phillips <asphilli@ucar.edu> wrote:
>>
>>> Hi Nisha,
>>> You can use the output from gc_inout:
>>> http://www.ncl.ucar.edu/Document/Functions/Built-in/gc_inout.shtml
>>> (See example #3)
>>> gc_inout will return data of type logical, and you can use that data in
>>> a where statement to mask out your data array.
>>> http://www.ncl.ucar.edu/Document/Functions/Built-in/where.shtml
>>> Then you can average over the remaining (non-missing) data.
>>>
>>> Hope that helps.. If not, please respond to ncl-talk..
>>> Adam
>>>
>>>
>>>
>>> On 07/13/2012 02:35 PM, Manisha Ganeshan wrote:
>>>
>>> Hello,
>>>
>>> Is there a NCL function that can compute the indices of all points
>>> lying inside a pre-defined polygon? For example, I have used
>>> gsn_add_polygon function to draw a polygon on a contour map, but I now wish
>>> to find an average value of a quantity over points lying inside this
>>> polygon.
>>>
>>> Thanks,
>>> Nisha
>>>
>>>
>>> _______________________________________________
>>> ncl-talk mailing list
>>> List instructions, subscriber options, unsubscribe:http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>>>
>>>
>>> --
>>> ______________________________________________________________
>>> 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
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> ncl-talk mailing list
>>> List instructions, subscriber options, unsubscribe:
>>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>>>
>>>
>>
>>
>
> --
> ______________________________________________________________
> 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
>
>
>
>

_______________________________________________
ncl-talk mailing list
List instructions, subscriber options, unsubscribe:
http://mailman.ucar.edu/mailman/listinfo/ncl-talk
Received on Tue Jul 17 12:16:03 2012