[gradsusr] [EXTERNAL] Re: Is there an easy way in GrADS to sample / aggregate a large data set instead of plotting it at full resolution?

Adams, Jennifer M. (GSFC-610.2)[ADNET SYSTEMS INC] jennifer.m.adams at nasa.gov
Tue Dec 15 12:56:54 EST 2020


Jeff wrote:
>>You can write a control file and adjust the nx and ny values in the XDEF and YDEF lines
>> so that GrADS attempts to plot your fields on a coarser grid.

This will only work if the grid is not rectilinear and you are using PDEF, where the XDEF/YDEF entries describe the destination grid for the pdef interpolation. Otherwise, the XDEF and YDEF entries must match the native grid.

The lterp() and skip() functions will work, but I suggest using ‘define’ to copy the original grid into memory first. This will mean you do the file I/O only once, and will speed up any function you apply to the original grid.
--Jennifer


On Tue, Dec 15, 2020 at 7:36 AM Robert Kuligowski <bob.kuligowski at noaa.gov<mailto:bob.kuligowski at noaa.gov>> wrote:
All,

     I have some netCDF files with 6501 lines and 18,000 columns that
I'm plotting in GrADS, and creating the .png  output files is taking a
long time.  I clearly don't need that much detail in the actual image,
so is there a simple way to sample or aggregate the data in GrADS before
plotting in order to make it render more quickly?  I looked through the
documentation but wasn't able to find the droids I'm looking for.  Thanks!

Cheers,

--
Bob Kuligowski, Ph.D.
Meteorologist
NOAA/NESDIS/Center for Satellite Applications and Research (STAR)

Mailing Address:
National Oceanic and Atmospheric Administration
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Bob Kuligowski
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5830 University Research Court
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College Park, MD 20740-3818

Phone:  (301) 683-3593
Fax  :  (301) 683-3616

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--
Jeff Duda, Research Scientist
University of Colorado Boulder
Cooperative Institute for Research in Environmental Sciences
NOAA/OAR/ESRL/Global Systems Laboratory
Boulder, CO
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