d3-jsnext/src/arrays/mean.js

d3, but futuristic

import { d3_number, d3_numeric } from '../math/number';

var d3$mean;

d3$mean = function(array, f) {
  var s = 0,
      n = array.length,
      a,
      i = -1,
      j = n;
  if (arguments.length === 1) {
    while (++i < n) if (d3_numeric(a = d3_number(array[i]))) s += a; else --j;
  } else {
    while (++i < n) if (d3_numeric(a = d3_number(f.call(array, array[i], i)))) s += a; else --j;
  }
  if (j) return s / j;
};

export { d3$mean };