chart = {
let height = 600;
let canvas = DOM.canvas(width, height);
let ctx = canvas.getContext("2d");
let radius = 2.5;
let xscale = d3
.scaleTime()
.domain(dateExtent)
.range([10, width - 10]);
combined.forEach(d => {
ctx.beginPath();
ctx.fillStyle = color(d.author);
ctx.arc(xscale(date(d)), yscale(d.repo), radius, 0, Math.PI * 2);
ctx.fill();
});
return canvas;
}