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Re: Array indexing: what is IDL doing? [message #60710 is a reply to message #60706]

Mon, 09 June 2008 06:02

Conor
Messages: 138
Registered: February 2007

Senior Member

On Jun 6, 5:15 pm, Jean H <jghas...@DELTHIS.ucalgary.ANDTHIS.ca>
wrote:
>> cx = n_elements(wx)
>> cy = n_elements(wy)
>> nx = n_elements(bigarr[*,0])
>> ind = transpose(rebin(wy,cy,cx))*nx + rebin(wx,cx,cy)
>> res = bigarr[ind]
>
> You don't have to use nx.
> res = bigarr[rebin(bigx,75,10000),rebin(bigy,10000,75)]
>
> Note that you must have the same number of elements in every subscripted
> dimension.
>
> Readhttp://www.dfanning.com/code_tips/asterisk.html
>
> Jean

On second thought, I'm now thoroughly confused. I don't understand
this bit:

res = bigarr[rebin(bigx,75,10000),rebin(bigy,10000,75)]

obviously rebin(bigx,75,10000) and rebin(bigy,10000,75) give you two
arrays with exactly opposite dimensions, so I don't understand how you
can index bigarr with these two arrays. Also, I'm not even sure what
IDL is doing when you index an array like that. My first thought was
that this was the equivelent of:

res = bigarr[ [rebin(bigx,75,10000),rebin(bigy,10000,75)] ]

But that obviously can't be the case because since they have different
dimensions, you can't concatenate the two arrays. So how does IDL
pull out an array index in your above example?

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[Message index]

		Re: Array indexing: what is IDL doing? By: Conor on Tue, 10 June 2008 07:16
		Re: Array indexing: what is IDL doing? By: Jean H. on Mon, 09 June 2008 10:12
		Re: Array indexing: what is IDL doing? By: Heinz Stege on Mon, 09 June 2008 08:34
		Re: Array indexing: what is IDL doing? By: Conor on Mon, 09 June 2008 06:02
		Re: Array indexing: what is IDL doing? By: Conor on Mon, 09 June 2008 05:56
		Re: Array indexing: what is IDL doing? By: Jeremy Bailin on Sat, 07 June 2008 06:12
		Re: Array indexing: what is IDL doing? By: Jean H. on Fri, 06 June 2008 14:15

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