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Re: Cannot allocate memory! [message #47037 is a reply to message #47032]

Tue, 17 January 2006 02:28

Craig Markwardt
Messages: 1869
Registered: November 1996

Senior Member

"Sheldon" <shejo284@gmail.com> writes:

> Thanks David,
>
> IDL does have a very good manual.
> I have a side question that I hope is short enough for you to answer.
> When looking at the other solutions for averaging large 3D arrays, I
> noticed something, namely that some synthax for depicting a 3D array
> took the form: array[50,50,3] where the third dimension is placed at
> the end and not the beginning: array[3,50,50].
> Coming over from Python, this seems a bit strange. What is the
> difference between these two?
> Doesn't IDL interpret former as a 50 dimensional array of 50 col x 3
> rows and the latter as a 3 dimensional array of 50 col x 50 rows?

It doesn't really matter whether you call an array index a row or a
column. There is more discussion here:

http://www.dfanning.com/misc_tips/colrow_major.html

I say it doesn't matter because most often, you must refer to the
array indices explicitly, so you can define what you mean by a row and
column yourself. The only time this is not true that I'm aware of is
when doing matrix multiplication with the "#" and "##" operators.
It's best just to verify which one is right for you.

For implementation efficiency, it may be important to know which array
elements are adjacaent. For an array, the elements ARRAY(*,J,K) are
contiguous in memory.

Craig

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

		Re: Cannot allocate memory! By: Liberum on Tue, 17 January 2006 09:43
		Re: Cannot allocate memory! By: Craig Markwardt on Tue, 17 January 2006 02:28
		Re: Cannot allocate memory! By: Liberum on Tue, 17 January 2006 00:56
		Re: Cannot allocate memory! By: David Fanning on Mon, 16 January 2006 13:09
		Re: Cannot allocate memory! By: Liberum on Mon, 16 January 2006 12:57
		Re: Cannot allocate memory! By: Liberum on Mon, 16 January 2006 12:47
		Re: Cannot allocate memory! By: Craig Markwardt on Mon, 16 January 2006 12:26
		Re: Cannot allocate memory! By: David Fanning on Mon, 16 January 2006 12:25

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