Re: PLOT procedure (was: Julian Day Numbers)

[Craig Markwardt <craigmnet(at)cow.physics.wisc.edu>]

James Tappin <sjt@star.sr.bham.ac.uk> writes:

> One real gotcha with Julian day numbers is if you try to use them for a 
> time axis on a plot.
> 
> It works fine for long time axes, but if you try looking at high-resolution 
> data things look really messy.
> 
> The problem is that PLOT converts to single-precision before converting 
> coordinates to data and this means that all values are truncated to the 
> nearest quarter day (for IEEE floats).

I agree that double precision plotting is important.  Sometimes you
just need it.  However I think that in this case you really want to
subtract a time offset anyway.  Consider that your axis labels will
never be pretty if you are using full Julian days.  [ for those that
don't know Julian days of this millenium number in the millions ].
You can put in your XTITLE or TITLE the time offset and be done with
it.

Nit-pickily yours,
Craig

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Craig B. Markwardt, Ph.D.         EMAIL:    craigmnet@cow.physics.wisc.edu
Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response
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