/// <summary>
/// Evaluates the harmonic mean.
/// Returns NaN if data is empty or if any entry is NaN.
/// </summary>
/// <param name="data">The data to calculate the harmonic mean of.</param>
/// <returns>The harmonic mean of the sample.</returns>
public static double HarmonicMean(this IEnumerable <double> data)
{
var array = data as double[];
return(array != null
? ArrayStatistics.HarmonicMean(array)
: StreamingStatistics.HarmonicMean(data));
}
