Re: Large File Plotting

[davidf(at)dfanning.com (David Fanning)]

Pavel Romashkin (promashkin@cmdl.noaa.gov) writes:

> >What is needed is
> > something that can detect file size and
> > only display to the pixel resolution of the
> > screen.
> 
> I think this is exactly what you need. At 1024 x 768, a monitor is
> capable of producing not better than 85 points per inch. Resample your
> large array to the desired resolution and plot it. PLOT will do this
> anyway (on a visual level), but a lot less efficiently.
> 
> If the axis you plot against is 5" long, then the maximum number of
> points you'll be able to see is < 500. Use CONGRID for plotting:
> 
> plot, congrid(a, 500)
> 
> works very fast.

Another suggestion along this line is to use the NSUM
keyword on the PLOT command. This indicates how many
adjacent points IDL is to average in order to reduce 
the number of plotted points.

If you are in to widget programming, I think you
should also be able to write something along the
lines of ZPLOT on my web page that allows you to
"zoom" into your data at different "resolutions".
Some combination of resampling the actual data
points and restricting the independent data range
should work. I don't think this would be too hard
to write.

Cheers,

David
-- 
David Fanning, Ph.D.
Fanning Software Consulting
Phone: 970-221-0438 E-Mail: davidf@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Toll-Free IDL Book Orders: 1-888-461-0155