import “../math/number”;

d3.mean = function(array, f) {

var n = array.length,
    a,
    m = 0,
    i = -1,
    j = 0;
if (arguments.length === 1) {
  while (++i < n) if (d3_number(a = array[i])) m += (a - m) / ++j;
} else {
  while (++i < n) if (d3_number(a = f.call(array, array[i], i))) m += (a - m) / ++j;
}
return j ? m : undefined;

};