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Re: [ferret_users] seting time-constant value to a map



Dear ferreter,

you can try ;
let var2=var1[l=1:12@ave]
let var3=var1-var1+var2

Then you chech if var3 has the correct time axis.

Also you can try

let var3=if var1 le 9999. then var1-var1+var2 else var1-var1+var2

Good luck,
Serena

On Mon, Jun 30, 2008 at 2:39 PM, DELCLAUX Francois <francois.delclaux@xxxxxxxxxxxxxxxxxxx> wrote:
Hi,
I suppose I was not clear in my question.
The aim of my question is to test the consequence of monthly rainfall seasonality on the outputs of
a hydrological model.

So I need  2 datasets:
- one with seasonality, ie12 different values
- one without seasonality, ie 12 identical values, each value being equal to the time average
of the 12 values, so as the sum is the same in the 2 cases.

Consequently, if var1 is the seasonal dataset and is described as
var1(i, j, 1) = val1
var1(i, j, 2) = val2
....
var1(j, j, 12)= val12

the 2nd dataset will be:
var2(i, j, 1) = var1(i, j, l=@ave)
var2(i, j, 2) = var1(i, j, l=@ave)
...
var2(i, j, 12) = var1(i, j, l=@ave)
So, for a given (i, j), all the L values of var2 will be identical and equal to the L average.

Then my question is:
how computing var2 from var1 ?

Sincerly

Francois Delclaux


Hi Francois,
To average over all of L, you can define a variable

 yes? let var2 = var1[L=@ave]

Then var2 will depend only on X and Y.

I'm not sure if that is what you wanted.  You can specify limits on the average, for instance var1[L=1:3@ave], or use a transformation, say a smoother. Make sure your X axis is defined as a MODULO axis, so that time wraps around from December to January. Then for instance you might define

 yes? let var3 = var1[L=@SBX:3]

which would replace each value with the average of the times at L-1, L, and L+1.
Or you could do an indefinite integral

 yes? let var4 = var1[L=@IIN]

Ansley

DELCLAUX Francois wrote:
Hi Ferret Users,

I have a 3D file with variable var1(I, J, L). This a monthly seasonal file where L varies from 1 to 12.

Now I would like to have time contant value for each value of  L i.e. a new variable var2 as follows:
var2(I, J, L) = var1(I, J, L@AVE) for L varying from 1 to 12.

What's the best procedure for getting var2  ?

Thanks




--
Francois DELCLAUX ------------------------------------------------------------
UMR HydroSciences Montpellier
Universite Montpellier II - Place Eugene Bataillon
Case courrier MSE
34095  Montpellier Cedex 5      FRANCE        http://www.hydrosciences.fr/   mailto: delclaux@xxxxxxxxxxxxxxxxxxx
Tel : (33) (0)4 67 14 90 11      Fax : (33) (0)4 67 14 47 74
------------------------------------------------------------




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