[ferret_users] The @DDC transformation in contour plots

[Kirsty Hanley <k.e.hanley@xxxxxxxxxxxxx>]

Hi,

I'm using Ferret v5.81 on Solaris. I have a NetCDF file containing a 
variable, swh, with X=1:120, Y=1:240 at 6 hourly timesteps for 1 year. I 
want to calculate and produce a contour plot of the time derivative of 
this variable at each point in space. I tried using the @DDC command:

yes? fill swh[l=2:28@DDC]

but received the following error:
**ERROR: dimensions improperly specified: must be a 2D region

If I specify a value of X and Y I can produce a line plot of the derivative:

yes? plot/i=60/j=60 swh[l=2:28@DDC]

Can the @DDC command only be used at a single point? If so, how can I 
calculate the time derivative over the entire region?

Any help much appreciated,
Kirsty

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Kirsty Hanley, PhD student
Room 2U06, Department of Meteorology,
University of Reading, Earley Gate
PO Box 243,
READING. RG6 6BB. U.K. 
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