Average function

[Charles Seman]

Loic,

If you try defining variables
(http://grads.iges.org/grads/gadoc/variable.html#new), it may work (are
your times (dates) different for each file? ...specifying the time
levels directly is then probably why you were able to do your working
example)

'set dfile 1'
...set lon/lat/height for file 1
'set t 1'
'define tas1 = ave(tas,t=2,t=1190)'
set dfile 2'
...set lon/lat/height for file 2
'set t 1'
'define tas2 = ave(tas,t=2,t=1190)'
'd tas1-tas2'

I hope this helps,
Chuck

Cottet, Loic (IFPRI) wrote:
> Hi all,
>
> I am trying to do the difference between 2 averages.
>
> It does not work:
>
> ga-> d (ave(tas,t=2,t=1190)-ave(tas.2,t=2,t=1190))
> Averaging.  dim = 3, start = 2, end = 1190
> Averaging.  dim = 3, start = 2, end = 1190
> Data Request Error: Invalid grid coordinates
>   World coordinates convert to non-integer grid coordinates
>     Variable = tas.2  Dimension = 3
> Operation Error:  Error from ave function
>   Error ocurred at column 22
> DISPLAY error:  Invalid expression
>   Expression = (ave(tas,t=2,t=1190)-ave(tas.2,t=2,t=1190))
>
> So I tried to put the same level (z=1)
>
> ga-> set z 1
> LEV set to 0 0
> ga-> d (ave(tas,t=2,t=1190)-ave(tas.2,t=2,t=1190))
> Averaging.  dim = 3, start = 2, end = 1190
> Averaging.  dim = 3, start = 2, end = 1190
> Data Request Error: Invalid grid coordinates
>   World coordinates convert to non-integer grid coordinates
>     Variable = tas.2  Dimension = 3
> Operation Error:  Error from ave function
>   Error ocurred at column 22
> DISPLAY error:  Invalid expression
>   Expression = (ave(tas,t=2,t=1190)-ave(tas.2,t=2,t=1190))
>
>
> It still has not worked,
>
> Can anyone help me out,
>
> I do not understand how else to do it because it works when I do a simple
> difference between those 2 temperature files:
>
> ga-> set z 1
> LEV set to 0 0
> ga-> d ((tas.2(t=1190)-tas.2(t=2)-(tas(t=1190)-tas(t=2))))
> Contouring: -25 to 15 interval 5
>
> I really would grateful to your help,
>
> Thanks a lot,
>
> Loic
>

--

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 Charles Seman                                charles.seman at noaa.gov
 U.S. Department of Commerce / NOAA / OAR
 Geophysical Fluid Dynamics Laboratory         voice: (609) 452-6547
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 Princeton, NJ  08540-6649            http://www.gfdl.noaa.gov/~cjs/
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