cdiff error!

[Prince K. Xavier]

Hi all,

I am trying to compute dU/dp (where U is the zonal wind, p is the
pressure) for all the 17 levels and 365 days. My script segment is as
follows...
.....
....
'set x 1 144'
'set y 1 73'
'set t 1 365'
'set z 1 17'

'define duz = cdiff(uwnd.1,z)'
'define dpz = cdiff(lev,z)'
....
....

but grads gives the following error.
-----------------------------------
Error from CDIFF:  Specified dimension non varying
Operation Error:  Error from cdiff function
  Error ocurred at column 1
DEFINE error:  Invalid expression.
----------------------------------

Can anyone figure out where I went wrong?

Thanks in advance,

regards
Prince
--
Prince K XAVIER
Centre for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
INDIA
http://caos.iisc.ernet.in/hpg/students/prince.html
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