<p>In <a href="https://github.com/mlpack/mlpack/pull/742#discussion_r72756774">src/mlpack/methods/preprocess/preprocess_describe_main.cpp</a>:</p>
<pre style='color:#555'>> + * @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);
</pre>
<p>Why not just write</p>
<p><code>skewness = M3 / (n*S3);</code></p>
<p>Besides, according to the formula at this <a href="http://www.macroption.com/skewness-formula/">page</a>, I think the equation of population skewness should be</p>
<p><code>std::sqrt(n) * M3 / (n*S3);</code></p>
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