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Re: [ferret_users] daily cumul to daily value
Le 26/02/2015 10:28, Delclaux Francois a écrit :
HI,
I have a file containing daily cumulative data. For exemple, if pi is
daily precipitation:
day 1: p1
day 2 : p1 + p2
day 3 : p1+ p2 +p3
...
day i : p1 + p2 + ... + pi-1 + pi
...
day 365 : p1 + p2 + ... + p365 = yearly precipitation
Now, I would like to calculate pi the daily precipitation, i.e.
day 1 : p1
day 2 : p2
day 3 : p3
...
day i : pi
...
day 365: p365
So, for each day, I have to substract the pi-1 value to the pi value.
Is it possible to do that with Ferret ?
Thanks in advance for any help
Hi,
You need to calculate a backward difference.
Using the transform SHF will do the job like this
yes? let rsum={2, 4, 6, 7, 8, 12, 12, 15}
yes? let inst=rsum-rsum[i=@shf:-1]
yes? list inst
VARIABLE : RSUM-RSUM[I=@SHF:-1]
SUBSET : 8 points (X)
1 / 1: ....
2 / 2: 2.000
3 / 3: 2.000
4 / 4: 1.000
5 / 5: 1.000
6 / 6: 4.000
7 / 7: 0.000
8 / 8: 3.000
Regards
Patrick
--
LSCE/IPSL, Laboratoire CEA-CNRS-UVSQ
Data Analysis and Visualization Engineer
ICMC - IPSL Climate Modelling Centre
--
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