vis = {
const svg = d3.select(DOM.svg(width, height));
svg.style("border", "1px solid #bbbbbb");
const g = svg.append("g").attr("id", "circles");
g.selectAll("circle")
.data(letters)
.enter()
.append("circle")
.attr("cx", d => x(d.frequency))
.attr("cy", d => y(d.points))
.attr("r", r)
.style("fill", d => color(d.type));
svg.append("g").attr("id", "annotation");
return svg.node();
}