Ordinary Least Squares

ols.js

// Ordinary Least Squares
function ols(points_, pointAccessor) {
  var points = points_.map(pointAccessor || function(d) { return d })
  var xmean = d3.mean(points, function(d) { return d[0] })
  var ymean = d3.mean(points, function(d) { return d[1] })
  var bNum = points
    .reduce(function(c, d) { return (d[0] - xmean) * (d[1] - ymean) + c }, 0)
  var bDenom = points
    .reduce(function(c, d) { return c + Math.pow(d[0] - xmean, 2) }, 0)
  var b = bNum / bDenom
  var a = ymean - b * xmean
  return {a: a, b: b}
}