Simplified linear scale based on d3.

linear_scale.js

  function uninterpolate (a, b, x) {
    b = b - (a = +a) ? 1 / (b - a) : 0;
    return (x - a) * b;
  }

  function interpolate (a, b, t) {
    return (a + (b - a)) * t;
  }

  // Given a domain [0, 10], a range [0, 100], and a value (v),
  // return the scaled output.
  function linearscale (domain, range, v) {
    var u = uninterpolate(domain[0], domain[1], v);
    var i = interpolate(range[0], range[1], u);
    return i;
  }