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Re: Arrays suck. Loops rock. [message #43047 is a reply to message #42948]

Tue, 08 March 2005 12:12

Benjamin Hornberger is currently offline

Benjamin Hornberger
Messages: 258
Registered: March 2004

Senior Member

Y.T. wrote:
> (I honestly fail to understand the provided example and am not at all
> sure that the two "rebins" are necessary. You are aware that 'rebin'
> performs interpolations, right?)

The rebin / reform steps are necessary if, e.g., you want to multiply a
3-d array [m, n, k] by a 2-d array [m, n] "layer by layer" in one array
operation rather than looping over k. Rebin won't interpolate in this
case, because you rebin from size 1 to size k (which just clones a value
k times). See the Dimension Juggling Tutorial at

http://www.dfanning.com/tips/rebin_magic.html

Some of the reform steps are necessary because of IDL's terrible
"feature" of cutting of trailing dimensions of size 1.

Thanks for the input! (I did run it multiple times, with similar
results, but I see that I should probably shut down as much other
activity on the computer as I can while timing these calculations.)

Benjamin

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[Message index]

		Re: Arrays suck. Loops rock. By: Y.T. on Tue, 08 March 2005 11:51
		Re: Arrays suck. Loops rock. By: JD Smith on Fri, 04 March 2005 12:59
		Re: Arrays suck. Loops rock. By: Benjamin Hornberger on Tue, 08 March 2005 12:12
		Re: Arrays suck. Loops rock. By: JD Smith on Mon, 14 March 2005 16:46

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