[gradsusr] cdiff

[Jennifer Adams]

On May 5, 2010, at 11:09 AM, Jeffrey Duda wrote:

> Muhammad,
> Unfortunately, you simply can't define a variable using cdiff in the  
> z-direction in Grads.
That's because GrADS constructs the defined object by looping over Z  
(and T and E if they are varying dims too). It's almost like a built- 
in zloop function -- you end up with a result that varies in Z, but  
the expression is evaluated at a fixed Z as it loops over all the  
specified Z levels.


> You can display a variable, but you'd have to write out the entire  
> formula for that variable in the display command.
That's correct. You can also write it out to a file, using gxout fwrite.
--Jennifer


>
> Jeff Duda
>
> On Wed, May 5, 2010 at 5:59 AM, Muhammad Afzaal <afzaalkarori at gmail.com 
> > wrote:
> Hello everybody
>
> I am using "cdiff" function along z-dimension to fine dvar/dz e.g
>
> -> 'set z 1 17'
> -> 'define dvar = cdiff(var,z)
>
> but I have following error
> Error from CDIFF:  Specified dimension non varying
> Operation Error:  Error from cdiff function
>   Error ocurred at column 1
> can anybody figure out the problem?
> Thanks
>
> -- 
> MUHAMMAD AFZAAL KARORI
>
>
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>
>
>
> -- 
> Jeff Duda
> Iowa State University
> Meteorology Graduate Student
> 3134 Agronomy Hall
> www.meteor.iastate.edu/~jdduda
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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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