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Re: For loop avoidance - getting indices of real space [message #81161 is a reply to message #81158]

Fri, 24 August 2012 02:32

lecacheux.alain
Messages: 325
Registered: January 2008

Senior Member

Le jeudi 23 août 2012 22:58:48 UTC+2, simu...@gmail.com a écrit :
> I have read and re-read until cross-eyed this post: http://www.idlcoyote.com/tips/forloops.html
>
>
>
> And yet, I still can't quite grasp at how I can solve my for loop problem. I think it might involve the use of modulo (MOD), but I'm not sure how. My question is, how can you grab the indices (i,j,k) of a 3D array in real space, and throw them into basically 3 1D arrays that is just a list of all the cells in the "proper" order (column-major).
>
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> Here is an example of what I mean:
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> pro testreader
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> xcells=15
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> ycells=10
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> zcells=20
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> ncells=xcells*ycells*zcells
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>
>
> data=dindgen(xcells,ycells,zcells)
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> coord=intarr(ncells,3)
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>
>
> index=0L
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> for k=0,zcells do begin
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> for j=0,ycells do begin
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> for i = 0,xcells do begin
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> coord(index,0)=i
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> coord(index,1)=j
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> coord(index,2)=k
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> index=index+1
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> endfor
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> endfor
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> endfor
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>
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> end
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> This is a really simple version of a complex problem I have. I have sets of different size boxes from an AMR MHD code, and I need to keep track of their indices, but I just want a list of all of the cells, not to drag around a bunch of smaller arrays or try to concatenate them into one giant sparse array (waste of space). I'm certain that someone must have had this problem before, but I can't find any other suggestions on this forum.

If I understand well your problem, a solution might be:

IDL> coord = [ [lindgen(xcells)#replicate(1,ycells*zcells)], $
IDL> [lindgen(ycells)#replicate(1,xcells*zcells)], $
IDL> [lindgen(zcells)#replicate(1,xcells*ycells)] ]
IDL> coord = reform(coord,ncells,3,/OVER)

alain.

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[Message index]

		Re: For loop avoidance - getting indices of real space By: Yngvar Larsen on Mon, 27 August 2012 03:37
		Re: For loop avoidance - getting indices of real space By: lecacheux.alain on Fri, 24 August 2012 07:41
		Re: For loop avoidance - getting indices of real space By: simulana on Fri, 24 August 2012 07:42
		Re: For loop avoidance - getting indices of real space By: simulana on Fri, 24 August 2012 07:25
		Re: For loop avoidance - getting indices of real space By: lecacheux.alain on Fri, 24 August 2012 02:32

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