[mlpack-git] [mlpack/mlpack] Descriptive Statistics command-line program (#742)

Tham notifications at github.com
Fri Jul 29 04:21:03 EDT 2016


> + * @param rowMean Mean of the given vector.
> + * @return Skewness of the given vector.
> + */
> +double Skewness(const arma::rowvec& input,
> +    const double& rowStd,
> +    const double& rowMean,
> +    const bool population)
> +{
> +  double skewness = 0;
> +  double S3 = pow(rowStd, 3);
> +  double M3 = SumNthPowerDeviations(input, rowMean, 3);
> +  double n = input.n_elem;
> +  if (population)
> +  {
> +    // Calculate Population Skewness
> +    skewness = n * M3 / (n * n * S3);

Why not just write

`skewness = M3 / (n*S3);`

Besides, according to the formula at this [page](http://www.macroption.com/skewness-formula/), I think the equation of population skewness should be

`std::sqrt(n) * M3 / (n*S3);`

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