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Re: Counting the lengths of continuous numbers in an array [message #61828 is a reply to message #61824]

Fri, 08 August 2008 14:28

mankoff
Messages: 131
Registered: March 2004

Senior Member

On Aug 8, 5:05 pm, andy.mcn...@gmail.com wrote:
> Howdy folks.
>
> Say I have the following array: [1, 2, 3, 4, 7, 8, 11, 13, 14, 17,
> 18, 19]
>
> How would I tell IDL to go through this array and return the array [4,
> 2, 1, 2, 3].....the lengths of the continuous groups of numbers in the
> array?
>
> Thanks!
> -Andy McNeel

I'm not sure how robust this is for other arrays, but I can get your
2nd array from your first like so, assuming the 1st array is "a". I
didn't test boundary cases (runlength of 1 on beginning or end) or
much else...

IDL> aa = [a[0],a,0]
IDL> b = where( (aa-shift(aa,1)) ne 1)
IDL> c = b-shift(b,1)
IDL> print, c[1:*]
4 2 1 2 3

-k.

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[Message index]

		Re: Counting the lengths of continuous numbers in an array By: andy.mcneel on Fri, 08 August 2008 14:41
		Re: Counting the lengths of continuous numbers in an array By: mankoff on Fri, 08 August 2008 14:28
		Re: Counting the lengths of continuous numbers in an array By: Brian Larsen on Mon, 11 August 2008 06:08

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