[gradsusr] cdiff function

[Adrian Scherzinger]

  Hi
I am looking for a function similar to cdiff, BUT instead of
"The result value at each grid point is the value at the grid point plus 
one minus the value at the grid point minus one."
i need a funktion that calculates:
"The result value at each grid point is the value at the grid point 
minus the value at the grid point minus one."

This is my problem:
Each timestep of my mm5 precipitation data set contains the integral of 
the precipitation since t=1. I want to plot a bar graph with the 
precipitation of each hour (not the integral). If I want to get the 
value only at time X, I need to calculate (rain at t=x)-(rain at t=x-1).
cdiff(rain,t) is not the solution.

Thanks for your help
Adrian

-- 
___________________________
Adrian Scherzinger
Stv. Leiter Wetterprognosen

Genossenschaft METEOTEST
Fabrikstrasse 14, CH-3012 Bern
Tel +41 (0)31 307 26 26
Fax +41 (0)31 307 26 10
adrian.scherzinger at meteotest.ch
http://www.meteotest.ch

********************************************************************
0900 57 61 52 (CHF 3.13/Min) im direkten Dialog mit dem Prognostiker
METEOFON - das persönliche Wettertelefon von METEOTEST (05-18 Uhr)
********************************************************************