@sgratzl/science/src/stats/mean.js

Scientific and statistical computing in JavaScript.

// Welford's algorithm.
export default function mean(x) {
  var n = x.length;
  if (n === 0) return NaN;
  var m = 0,
      i = -1;
  while (++i < n) m += (x[i] - m) / (i + 1);
  return m;
};