comp.lang.idl-pvwave archive: archive » Re: PLOT procedure (was: Julian Day Numbers)

Home » Public Forums » archive » Re: PLOT procedure (was: Julian Day Numbers)

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Re: PLOT procedure (was: Julian Day Numbers) [message #22600 is a reply to message #22597]

Tue, 21 November 2000 00:00

Craig Markwardt
Messages: 1869
Registered: November 1996

Senior Member

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

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

Report message to a moderator

[Message index]

		Re: PLOT procedure (was: Julian Day Numbers) By: Martin Schultz on Wed, 22 November 2000 00:00
		Re: PLOT procedure (was: Julian Day Numbers) By: Craig Markwardt on Tue, 21 November 2000 00:00
		Re: PLOT procedure (was: Julian Day Numbers) By: Paul van Delst on Tue, 21 November 2000 00:00

Previous Topic:	lego tiled image (how to make?)
Next Topic:	LAPACK and IDL?

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Tue Dec 02 07:24:44 PST 2025

Total time taken to generate the page: 0.72178 seconds