<p>In <a href="https://github.com/mlpack/mlpack/pull/742#discussion_r73781904">src/mlpack/methods/preprocess/preprocess_describe_main.cpp</a>:</p>
<pre style='color:#555'>> + 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);
> + }
> + else
> + {
> + // Calculate Sample Skewness
> + skewness = n * M3 / ((n-1) * (n-2) * S3);
</pre>
<p><a href="https://github.com/stereomatchingkiss" class="user-mention">@stereomatchingkiss</a> I imitated the result from <a href="https://support.office.com/en-US/article/SKEW-function-BDF49D86-B1EF-4804-A046-28EAEA69C9FA">excel</a>.<br>
This formula appears near the bottom of this <a href="http://www.macroption.com/skewness-formula/">page</a></p>
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