Circular Variance

mctad.circularVariance() accepts an Array of angles (radians as numbers or strings, or degrees as strings only, in the form "47.3°") and returns their variance in radians as a Number. Relies on mctad.meanResultantLength(). From Kanti V. Mardia & Peter E. Jupp, "Directional Statistics", Wiley, 2000

mctad.circularVariance = function (data) {

The circular variance is undefined if the data is not in an Array of 1 or more elements.

if (!Array.isArray(data) || data.length === 0) { return undefined; }

Mardia & Jupp equation (2.3.3)

return 1 - mctad.meanResultantLength(data); };