Re: [Boost-users] how to calculate the Sample standard deviation using accumulators

Subject: Re: [Boost-users] how to calculate the Sample standard deviation using accumulators
From: Victor Yankee (victor.whiskey.yankee_at_[hidden])
Date: 2012-01-18 12:36:18

Hello Marshall,

>On Jan 17, 2012, at 3:38 PM, Victor Yankee wrote:
>
>> How can I calculate the Sample Standard Deviation over a std::vector of
doubles using accumulators?
>>
>>Or is there a faster way in boost math or some such?
>
>
>Google is your friend (second hit for "boost accumulator standard
deviation"):
>
http://stackoverflow.com/questions/7616511/calculate-mean-and-standard-deviation-from-a-vector-of-samples-in-c-using-boos
>and
http://stackoverflow.com/questions/4316716/is-it-possible-to-use-boost-accumulators-with-vectors
>
>
>       accumulator_set<double, stats<tag::variance> > acc;
>       for_each(a_vec.begin(), a_vec.end(), bind<void>(ref(acc), _1));
>
>       cout << mean(acc) << endl;
>       cout << sqrt(variance(acc)) << endl;

But this is the POPULATION standard deviation (variance divided by N) I
think.

What I was asking for was how to calculated the SAMPLE standard deviation
(variance devided by N-1).

Thanks,
Vic