Mean Resultant Length

From Kanti V. Mardia & Peter E. Jupp, "Directional Statistics", Wiley, 2000

mctad.meanResultantLength = function (data) {

The mean resultant length 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 2.2.3

var C_bar, S_bar, R_bar, acc = { cos: 0, sin: 0 }; for (var i = 0; i < data.length; i++) { acc.cos += Math.cos(mctad.toRadians(data[i])); acc.sin += Math.sin(mctad.toRadians(data[i])); } C_bar = (acc.cos / data.length); S_bar = (acc.sin / data.length); R_bar = Math.sqrt(Math.pow(C_bar, 2) + Math.pow(S_bar, 2)); return R_bar; };