[ncl-talk] extract_Data_from_polygon

[Kunal Bali]

I am not getting it exactly how to do this one.
Could any one please help me out to do this.

Kunal Bali
Research Scholar
Radio & Atmospheric Science Division
CSIR - National Physical Laboratory
New Delhi - 110012
India





On Fri, May 27, 2016 at 6:12 PM, Guido Cioni <guidocioni at gmail.com> wrote:

> Once you have the correct variable you can write it to an CSV file by
> using the write table function.
>
>  alist=[/clon,clat,var2/]
>  write_table(“file.csv”,"w",alist,”%f,%f,%f,%f")
>
> Guido Cioni
> http://guidocioni.altervista.org
>
> On 27 May 2016, at 14:24, Kunal Bali <kunal.bali9 at gmail.com> wrote:
>
> Dear Guido
>
> Thanks for the information.
> Actually, I need to extract the data as ASCII or CSV file of the selected
> polygon box
>
>
>
> Kunal Bali
> Research Scholar
> Radio & Atmospheric Science Division
> CSIR - National Physical Laboratory
> New Delhi - 110012
> India
>
>
>
>
>
> On Fri, May 27, 2016 at 5:35 PM, Guido Cioni <guidocioni at gmail.com> wrote:
>
>> Dear Kunal,
>> I didn’t answer to the first email because I am not really familiar with
>> shapefile and masking over nations boundaries, but I guess there is a
>> lot of documentation on the website. Is your a polygon just an
>> approximation because you don’t know how to mask using the shape file or is
>> it really what you wanted to do?
>>
>> In order to extract the data you can either create a new variable where
>> you mask the region outside of the polygon or where you put all the data
>> inside of the polygon. I would use the first approach, since what you get
>> is a variable with the same dimensions, but maybe the second one is easier.
>> Since you have two arrays with lon,lat coordinates can’t you just create
>> a new variable, called var2, which is a subset of var?
>>
>> Assuming that var has dimension (time, lat, lon) you can simply do that
>>
>> var2=var(:,{lat},{lon})
>>
>> The {} means that you are using coordinate indexing, it should work also
>> with array although I’m not 100% sure. With this method you will get a
>> variable with different dimensions. Otherwise you can try to mask using
>> logical staments. Assuming you have (clon,clat) coordinates in your file
>> (I used different names because of your definition in the script) you can
>> try something similar
>>
>> var2=mask(var, lon.ge.min(clon) .AND. lon.le.max(clon) .AND.
>> lat.ge.min(clat) .AND. lat.le.max(clat), False)
>>
>> Cheers
>>
>>
>> Guido Cioni
>> http://guidocioni.altervista.org
>>
>> On 27 May 2016, at 12:31, Kunal Bali <kunal.bali9 at gmail.com> wrote:
>>
>> Dear NCL
>>
>> I tried to make the  polygon of the selected region. I don't know i did
>> it correctly or not, please let me know is it correct way to do or not.
>>
>> Second thig is that I need to extract the data from selected polygon.
>> Could anyone please let me know how to do it ?
>>
>>
>> Regards
>> Kunal Bali
>>
>>
>>
>>
>>
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>>
>
>
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