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From Mikkel Meyer Andersen <m...@mikl.dk>
Subject Re: [math] SummaryStatistics.setVarianceImpl Usage
Date Sun, 16 Oct 2011 14:43:38 GMT
Dear Warren,

Could you provide values for the scores-variable in the current
example making it possible to reproduce?

Are you in fact using version 1.2 as reflected by the link you gave?
Or which version are you using?

Cheers, Mikkel.

2011/10/16 Warren Tang <warren.c.tang@gmail.com>:
> Hello, everyone
>
> I'm trying to get a "population standard deviation
> <http://commons.apache.org/math/api-1.2/org/apache/commons/math/stat/descriptive/moment/StandardDeviation.html>"
> (non-bias-corrected) from SummaryStatistics.
>
> This is what I did:
>
> SummaryStatistics stats = new SummaryStatistics();
> stats.setVarianceImpl(new Variance(false)); //use "population variance"
> ( sum((x_i - mean)^2) / n )
> for(int i : scores) {
> stats.addValue(i);
> }
> double sd = stats.getStandardDeviation();
>
> However, the value of "sd" is "NaN". How can I do it correctly?
>
> --
> Regards,
> Warren Tang <http://blog.tangcs.com>
>

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