[gradsusr] how to obtain areal average in a given shapefile

[Jennifer Adams]

On Feb 23, 2011, at 2:37 AM, Marcelino II Villafuerte wrote:

> Hi all,
>
> Aside from reading and writing a shapefile in grads (http://www.iges.org/grads/gadoc/gadocindex.html 
> )
> is it also possible to produce an areal average [aave() function] of  
> a specific parameter e.g. rainfall,
> in a specific province or region prescribed in a shapefile?
No. The contents of shapefiles are treated in GrADS as graphical  
elements (points, lines, or polygons) to be drawn in a geo-registered  
context.

To do what you want, you would have to draw the polygon that  
corresponds to the province or region of interest, then overlay a  
'gxout grid' plot of your data, and then use the 'q pos' interface to  
manually flag grid points that you want to include in your area  
average, creating a customized mask. Take a look at 'set defval'. This  
is not a straightforward task, and would require a bit of script  
writing.
--Jennifer



>
>
> Thanks in advance!
> -- 
> ---------------------------------------
> Marcelino Q. Villafuerte II
> Weather Specialist I
> IAAS, CAD
> PAGASA-DOST
>
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--
Jennifer M. Adams
IGES/COLA
4041 Powder Mill Road, Suite 302
Calverton, MD 20705
jma at cola.iges.org



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