Re: Values inside a polygon

Hi Manisha,
When I ran your script an hour ago using NCl 6.1.0-beta, I was getting
95 points that were being returned as True from gc_inout:
inout = gc_inout(lat_new, lon_new, latcity, loncity)
print(num(ind(inout)))
exit

However, I noticed that upon reading in your grib file I was getting an
error message:
fatal:Premature end-of-file, file appears to be truncated

I didn't think anything of the error message as your script seemed to be
working. I have never seen that error message before, and it makes me
wonder if something is amiss with your .grb file. I tried rerunning your
script using ncl v6.0.0. I did get the same error message, but this time
I see that gc_inout is not returning any True values, as you were
experiencing.

I see from your latest email you have gotten around the issue. If you
need us to investigate any further let ncl-talk know. Adam

On 07/17/2012 12:15 PM, Manisha Ganeshan wrote:
> 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
> <mailto: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 <mailto: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 <mailto: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
>>>>
>>>>
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>>>
>>> --
>>> ______________________________________________________________
>>> Adam Phillipsasphilli@ucar.edu <mailto:asphilli@ucar.edu>
>>> NCAR/Climate and Global Dynamics Division(303) 497-1726 <tel:%28303%29%20497-1726>
>>> P.O. Box 3000
>>> Boulder, CO 80307-3000http://www.cgd.ucar.edu/cas/asphilli
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> ncl-talk mailing list
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>>>
>>>
>>
>>
>
> --
> ______________________________________________________________
> Adam Phillipsasphilli@ucar.edu <mailto:asphilli@ucar.edu>
> NCAR/Climate and Global Dynamics Division(303) 497-1726 <tel:%28303%29%20497-1726>
> P.O. Box 3000
> Boulder, CO 80307-3000http://www.cgd.ucar.edu/cas/asphilli
>
>
>
>
>
>
> _______________________________________________
> ncl-talk mailing list
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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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Received on Tue Jul 17 12:55:23 2012