[ncl-talk] How to pick out the grids in a chosen area from a polar stereographic projection dataset?

[Guido Cioni]

You can use ind_resolve to reshape the indices of the box and then use them to subset. I guess something like this would work (untested)

 dims_lat = dimsizes(latitude)
 dims_lon = dimsizes(longitude)

 lon1d = ndtooned(longitude)
 lat1d  = ndtooned(latitude) 

 box_lon = ind(lon1d.ge.min_lon .AND. lon1d.le.max_lon )
 box_lat = ind(lat1d.ge.min_lat .AND. lat1d.le.max_lat)

 inds_lon = ind_resolve(box_lon, dims_lon)
 inds_lat  = ind_resolve(box_lat, dims_lat)

 xbox=x(:,inds_lat,inds_lon)


Guido Cioni
http://guidocioni.altervista.org <http://guidocioni.altervista.org/> 




> Il giorno 23 ago 2016, alle ore 04:53, 林祥 <xianglin72 at icloud.com> ha scritto:
> 
> Hey Cioni,
> 
>     Thanks for your reply.   The longitude and latitude array is 2-dimensional, so I rewrite the following scripts
> 
>    lon1d = ndtooned(longitude)
>    lat1d  = ndtooned(latitude)
>    x1d    = ndtooned(x)
> 
>    box_id = ind(lon1d.ge.min_lon .AND. lon1d.le.max_lon .AND. lat1d.ge.min_lat .AND. lat1d.le.max_lat)
>   ;box_id = ind(lat1d.ge.min_lat .AND. lat1d.le.max_lat)   ; the result is same as the above line
> 
>    xlat    = lat1d(box_id)
>    xlon   = lon1d(box_id)
>    xbox   =   x1d(box_id)
> 
>  No I have picked out the data in the chosen area. But I am puzzled by plotting the contouring map for xbox.
> Should I have to deal with the array of xbox like the separated station datas?
> 
> Thanks
> 
> 
> Lin
> 
> 
> 
> 
>> 在 2016年8月23日，00:12，Guido Cioni <guidocioni at gmail.com <mailto:guidocioni at gmail.com>> 写道：
>> 
>> Hey Lin,
>> when dealing with non-monotonic arrays I usually employ the ind function, so I don’t understand why is not working for you…
>> 
>> If you have, say, lon and lat arrays (this assume to have them 1-Dimensional, otherwise it gets fishy…).
>> 
>> min_lon= -50.
>> max_lon= -70.
>> min_lat= -180.
>> max_lat= -180.
>> box_lon= ind(lon.ge.min_lon .AND. lon.le.max_lon)
>> box_lat= ind(lat.ge.min_lat .AND. lat.le.max_lat)
>> 
>> should give you exactly all the indices inside the user-prescribed area. Then you can subset using
>> 
>> var_box=var(:,box_lat,box_lon)
>> 
>> Please be reminded that box_values will have different dimensions, since it is a subset of the original variable.
>> Cheers,
>> 
>> Guido Cioni
>> http://guidocioni.altervista.org <http://guidocioni.altervista.org/> 
>> 
>>> On 22 Aug 2016, at 01:13, 林祥 <xianglin72 at icloud.com <mailto:xianglin72 at icloud.com>> wrote:
>>> 
>>> <latitude.csv>
>> 
> 

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