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Re: (more) Efficient way to generate an array whose elements are the distance from the center [message #80702 is a reply to message #80701]

Fri, 06 July 2012 13:53

Lajos Foldy
Messages: 176
Registered: December 2011

Senior Member

On Friday, July 6, 2012 10:37:35 PM UTC+2, Mike F. wrote:
> Hello all.
>
> I'm new to IDL (and coding in general), and I'm looking to find a more efficient way to generate an nxn array where each element is the distance from the center of the array.
>
> 3 x 3 Ex: 1.4 1 1.4
> 1 0 1
> 1.4 1 1.4
>
> All I can think of on my own is a nested FOR loop as such:
>
> FOR i = 0l, (n - 1) DO BEGIN
> FOR j = 0l, (n - 1) DO BEGIN
>
> plane[i,j] = SQRT( (i-n/2.)^2 + (j - n/2.)^2 )
>
> ENDFOR
> ENDFOR
>
> From what I've read on IDL forums, nested FOR loops are the pinnacle of sin, and I'd like to be a bit more pious if possible.
>
> Any tips would be appreciated!

Look up DIST and SHIFT in the docs:

IDL> print, shift(dist(3),1,1)
1.41421 1.00000 1.41421
1.00000 0.00000 1.00000
1.41421 1.00000 1.41421

regards,
Lajos

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[Message index]

		Re: (more) Efficient way to generate an array whose elements are the distance from the center By: Mike F. on Fri, 06 July 2012 14:05
		Re: (more) Efficient way to generate an array whose elements are the distance from the center By: Lajos Foldy on Fri, 06 July 2012 13:53
		Re: (more) Efficient way to generate an array whose elements are the distance from the center By: Michael Galloy on Sun, 08 July 2012 08:39

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