New Splines!

<!DOCTYPE html>
<meta charset="utf-8">
<canvas width="960" height="500"></canvas>
<script src="d3.min.js"></script>
<script>

var points = [
  [  0,   0],
  [ 90,   0],
  [180,  15],
  [270,  73],
  [360, 293],
  [450, 308],
  [540, 323],
  [630, 367],
  [720, 411],
  [810, 425],
  [900, 425]
];

var canvas = document.querySelector("canvas"),
    context = canvas.getContext("2d");

var margin = {top: 30, right: 30, bottom: 30, left: 30},
    width = canvas.width - margin.left - margin.right,
    height = canvas.height - margin.top - margin.bottom,
    radius = 3.5;

var color = d3.scale.category10()
    .domain([
      "cubic",
      "catmull-rom:0.0",
      "catmull-rom:0.5",
      "catmull-rom:1.0"
    ]);

var line = d3.shape.line()
    .context(context);

context.translate(margin.left, margin.top);

// Axes
context.moveTo(0.5, height + 0.5);
context.lineTo(0.5, 0.5);
context.moveTo(0.5, height + 0.5);
context.lineTo(width + 0.5, height + 0.5);
context.stroke();

// Points
points.forEach(function(d) {
  context.beginPath();
  context.moveTo(d[0] + radius, d[1]);
  context.arc(d[0], d[1], radius, 0, 2 * Math.PI, true);
  context.fill();
});

// Splines
color.domain().forEach(function(i) {
  var parts = i.split(":"), name = parts[0], value = +parts[1];
  context.beginPath();
  line.interpolate(name, value)(points);
  context.lineWidth = 1.5;
  context.strokeStyle = color(i);
  context.stroke();
});

</script>