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Re: simple array math question [message #33786 is a reply to message #33713]

Mon, 27 January 2003 11:54

Craig Markwardt
Messages: 1869
Registered: November 1996

Senior Member

JD Smith <jdsmith@as.arizona.edu> writes:

> On Sun, 26 Jan 2003 13:11:31 -0700, Craig Markwardt wrote:
>
>
>> Heinz Stege <reply_to_posting@arcor.de> writes:
>>>
>>> Thanks a lot for this very instructive contribution! Since the
>>> proposal of the intarr() method was from me, the NG may allow me to
>>> state this here.
>>>
>>> REBIN(REFORM(...)) is the better alternative. This is obvious now.
>>
>> "Better" can be defined in a lot of ways. Your solution is by far the
>> most readable way, in my view, to extend arrays. And it's cool because
>> nobody seems to have discovered it before!
>>
>> Speed is only king when you need a king.
>
>
> Well put. Ideally, IDL would have an intrinsic, readable, "inflate"
> operator to do what we're all doing in roundabout, quasi-readable ways
> right now. Maybe something like:
>
> IDL> a=findgen(10,12,14)
> IDL> g=a[3;7]*randomu(sd,10,12,7,14)

Yorick, a language very similar to IDL, but sadly not very popular,
has some very cool ways to do this. The first is a "pseudo-index"
which automatically introduces dimensions of length one.

a[*,*,-,*] would be a 10x12x1x14 array, the "-" introducing the extra
dimension. Yorick has a separate meaning for the "*"
operator but I mean it here in the normal IDL sense.

The second thing is "broadcasting," which automatically extends
dimensions of length 1. Thus, in the expression,

a[*,*,-,*] * randomu(sd,10,12,7,14)

The 3rd dimension is automatically extended to length 7 by replicating
A. Someone has already thought about these things (Yorick's author,
David Munro), and they are very cool!

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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[Message index]

		simple array math question By: Sean Raffuse on Thu, 16 January 2003 12:05
		Re: simple array math question By: Pepijn Kenter on Tue, 28 January 2003 05:40
		Re: simple array math question By: Craig Markwardt on Mon, 27 January 2003 11:54
		Re: simple array math question By: JD Smith on Mon, 27 January 2003 10:20
		Re: simple array math question By: JD Smith on Mon, 27 January 2003 10:00
		Re: simple array math question By: Craig Markwardt on Sun, 26 January 2003 12:11
		Re: simple array math question By: Craig Markwardt on Fri, 24 January 2003 11:29
		Re: simple array math question By: Pepijn Kenter on Fri, 24 January 2003 07:50
		Re: simple array math question By: K. Bowman on Fri, 24 January 2003 06:38

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