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Re: days of the week [message #29836]

Thu, 21 March 2002 09:01

Craig Markwardt
Messages: 1869
Registered: November 1996

Senior Member

"Mark Hadfield" <m.hadfield@niwa.co.nz> writes:

> "Craig Markwardt" <craigmnet@cow.physics.wisc.edu> wrote in message
> news:ong02v434v.fsf@cow.physics.wisc.edu...
>
>> P.S. I think the built-in JULDAY function is the one of the most
>> dangerous function I have ever seen. It measures *calendar dates*
>> from *noon* by gosh!
>
> I couldn't agree more.
>
>> It also doesn't handle fractional days...
>
> Not true in recent versions...
>
> IDL> print, julday(03,21,2002)
> 2452355
> IDL> print, julday(03,21,2002,10,23,30)
> 2452354.9
>
> But that weird argument order (month, day, year, ...) is what I
> *really* hate.

That is true, and the irony here is that JULDAY came from Numerical
Recipes, and other criticisms about code quality aside, those NR guys
are *astronomers* gosh darnit!

The following is totally unintuitive to me:

IDL> print, julday(3d,21d,2002d), format='(D30.3)'
2452355.000
;; Now, how about "one second" later
IDL> print, julday(3d,21d,2002d,00d,00d,01d), format='(D30.3)'
2452354.500

It's because in one case the calendar dates are measured from noon,
and in the other they are measured from midnight.

Craig

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

		Re: days of the week By: Craig Markwardt on Thu, 21 March 2002 09:01
		Re: days of the week By: Craig Markwardt on Thu, 21 March 2002 09:01
		Re: days of the week By: Doug Rowland on Thu, 21 March 2002 07:34
		Re: days of the week By: the_cacc on Thu, 21 March 2002 03:21
		Re: days of the week By: Mark Hadfield on Wed, 20 March 2002 14:20
		Re: days of the week By: Mark Hadfield on Wed, 20 March 2002 14:26
		Re: days of the week By: Ed Wright on Wed, 20 March 2002 09:17
		Re: days of the week By: Randall Skelton on Wed, 20 March 2002 09:42
		Re: days of the week By: David Fanning on Wed, 20 March 2002 08:59
		Re: days of the week By: David Fanning on Wed, 20 March 2002 08:49
		Re: days of the week By: eddie haskell on Wed, 20 March 2002 08:25
		Re: days of the week By: Craig Markwardt on Wed, 20 March 2002 08:26
		Re: days of the week By: David Fanning on Wed, 20 March 2002 07:47
		Re: days of the week By: David Fanning on Wed, 20 March 2002 07:12
		Re: days of the week By: Martin Downing on Mon, 25 March 2002 09:07

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