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Re: Counting the lengths of continuous numbers in an array [message #61824]

Fri, 08 August 2008 14:41

andy.mcneel
Messages: 3
Registered: August 2008

Junior Member

On Aug 8, 4:28 pm, mankoff <mank...@gmail.com> wrote:
> 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.

This worked beautifully. Thanks! -Andy

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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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