Re: [ferret_users] Reduce the size of the data

[Andrew Wittenberg - NOAA Federal <andrew.wittenberg@xxxxxxxx>]

Peter,

For user-defined variables, Ferret defaults to double precision output.  If your input file is FLOAT or INT, then this will increase the output file size.

To reduce the output precision and save space, see:

http://ferret.pmel.noaa.gov/Ferret/documentation/users-guide/commands-reference/SAVE#SAVE_OUTPUT_TYPE

Usually early in my Ferret session, I do:

SET LIST/OUTTYPE=float

​which changes the default output ​type to single precision -- halving the file size.

​Andrew​

PS: Ansley: Please correct a typo on the above page, which has a spurious leading "/": "/SET LIST/OUTTYPE=" 

---
Dr. Andrew T. Wittenberg
Physical Scientist (NOAA Federal)
Climate Variations and Predictability Group
NOAA Geophysical Fluid Dynamics Laboratory
201 Forrestal Road
Princeton, NJ 08540-6649
USA

​​

Web: http://www.gfdl.noaa.gov/~atw

On Fri, Mar 17, 2017 at 10:13 AM, Peter Szabo <szabpet83@xxxxxxxxx> wrote:

Dear Nicolas,

I also wonder why my file sizes always become way (usually double or 4
times) larger than the original ones even if they share still the same
dimensions.

The original file is 1.5 MB, while the saved out one with just values
masked out are 6.0 MB. It is the simplest operation with a short
formula and still making the file size way larger.

Regards,
Peter Szabo

!FERRET v6.9
!Linux 2.6.32-431.5.1.el6.x86_64 32-bit - 04/03/14

use TMAX7100mon_14_CCLIM.nc
use NATER_mask.nc !THIS CONSISTS OF 1 TIME DIMENSION AND 1s WHERE THE
MASK IS VALID
let maszkHU=mask[d=2,gx=longitude,gy=latitude,l=1]
let txHU=maszkHU*tx[d=1]
save/.. txHU

2017-03-17 11:26 GMT+01:00, Nicolas Freychet <nicolas.freychet@xxxxxxxxx>:
> Hi all,
>
> I computed the daily minimum of temperature based on 3h datasets (8
> values/day), using the methodology (by steps of 8, I pick up the minimum
> temperature, and associate it to the first step to record it)
>
>
> define axis/calendar=julian/t=01-jan-1979:31-dec-1995:3/units=hours tmodel
> repeat/range=1:49672:8/name=it (  let
> tmin=temp[l=`it`]*0+tmin[l=`it`:`it+7`@min] ; save/append/file=Output.nc
> Tmin[l=`it`,gt=tmodel@asn] )
>
> The problem is my output file is much bigger than it should. I got the
> impression that Ferret is recording the whole "formula" and not just the
> value of Tmin. Is there a way to solve that?
>
> (my way to define Tmin may not be optimal though, that may cause the
> problem...)
>
> Thanks,
> Nicolas
>
>
>
> ----------------------------------------------------
> Nicolas Freychet
> PDRA, School of Geosciences
> University of Edinburgh
> ----------------------------------------------------
>