Mean Direction

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

mctad.meanDirection = function (data) {

The mean direction 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 2.2.4

var C_bar, S_bar, θ_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); if (C_bar >= 0 ) { θ_bar = Math.atan(S_bar/C_bar); } else { θ_bar = Math.atan(S_bar/C_bar) + mctad.π; } return θ_bar; };