Re: Set of columns from 3D dataset using 'getind_latlon2d'

Hi Jakob,

What you need to do is convert these index values into values that
index into a 1D array.

Assume that:

  nlayer = 40
  nlat = 400
  nlon = 550

;---Convert to indexes into a 1D array dimensioned nlat*nlon.
  idx1d = (idx(:,0)*nlon) + idx(:,1)

;---Convert model data to 2D array (nlayer x nlat*nlon)
  data2d = onedtond(ndtooned(data),(/nlayer,nlat*nlon/))

;---Get new values at idx1d locations
  new_data2d = data2d(:,idx1d)

--Mary

On Jun 11, 2010, at 3:13 PM, Jakob Tendel wrote:

> Hi,
>
> SITUATION:
> I have model data on a (40layer x 400lat x 550lon) grid, converted
> out of a rotated lat/lon grid. I have lat2D and lon2D fields for
> this data.
>
> I want to extract whole vertical columns of this data at a set of
> specific coordinates (lat/lon). I use the function 'getind_latlon2d'
> to give me the indices into lat2D/lon2D for the nearest grid points
> to these locations, which is acceptable.
>
> PROBLEM:
> The output of 'getind_latlon2d' has the form (n_points x 2), a set
> of indices into the rightmost two dimensions of my data. I want to
> use these indices to subscript into the data to give me a set of
> columnar data for each of the locations, i.e. a 2D array. However,
> when I subscript the data in the form 'data( : , idx(:,0) , idx(:,
> 1) ), I get a 3D array in return. What I actually want is the
> horizontal diagonal of this array (:,0,0), (:,1,1,),(:,2,2) etc.
>
> QUESTION:
> Is there a sensible way of extracting a set of vertical columns out
> of 3D data and writing them into a 2D array using proper array
> indexing notation? Yes of course this can be done with loops but
> that is horribly slow and not really the point, is it?
>
> Thanks for any tips,
>
> Jakob
>
>
>
> --
> Jakob Tendel Phone 303 497 2713
> Research Applications Laboratory Office 3106b
> National Center for Atmospheric Research Building FL2
> 3450 Mitchell Lane
> Boulder CO 80301
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Received on Sun Jun 13 07:12:03 2010