MathGroup Archive 2004

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Re: Counting Runs


On Nov 4, 2004, at 1:50 AM, Gregory Lypny wrote:

> Looking for an elegant way to count runs to numbers in a series.
> Suppose I have a list of ones and negative ones such as
> 	v={1,1,1,-1,1,1,1,1,1,-1,-1,-1,-1,1}.
> I'd like to create a function that counts the number of runs of 1s and
> -1s, which in this case is 3 and 2.
>

I'm not sure about elegance but:

With[{lst=#[[1]]&/@Split[v]},{#,Count[lst,#]}&/@Union[lst]]

will do what you want.

Regards,

Ssezi


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