[ferret_users] subsampling as qualifier

[Patrick Brockmann <Patrick.Brockmann@xxxxxxxxxxxx>]

Hi,

There is already a way to control subsampling by applying strides on 
axis. This is very usefull
to display quickly maps with quite large grids (1442x1022 for example).

This is described in paragraph 2.1.1 NetCDF data and strides
http://ferret.pmel.noaa.gov/Ferret/documentation/users-guide/data-set-basics/NETCDF-DATA#_VPID_39

Now, I would find very convenient to control this directly from a 
qualifier and not by previous
set/cancel of strided axis.

Something like

yes? use curvilinear.nc
yes? shade/stride=4 var, lon2D, lat2D
yes? shade/stride=2 var, lon2D, lat2D

Rather than

yes? use curvilinear.nc
yes? SET AXIS/STRIDE=4 `var,RETURN=xaxis`
yes? SET AXIS/STRIDE=4 `var,RETURN=yaxis`
yes? shade var, lon2D, lat2D
yes? CANCEL AXIS/STRIDE `var,RETURN=xaxis`
yes? CANCEL AXIS/STRIDE `var,RETURN=yaxis`
yes? SET AXIS/STRIDE=2 `var,RETURN=xaxis`
yes? SET AXIS/STRIDE=2 `var,RETURN=yaxis`
yes? shade var, lon2D, lat2D

Is is possible ?

And to go further, does a mechanism to set this stride value
according to the size of the target image could be implemented ?
Because there is finally no point to process all points of variables if
the map is displayed as a small image. Just a thought...

Best regards
Patrick

--
LSCE/IPSL, Laboratoire CEA-CNRS-UVSQ
Data Analysis and Visualization Engineer
ICMC - IPSL Climate Modelling Centre
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