Now that text is out of the way, let's look at something much more interesting--shape primitives, which we use to create everything from the bars in a bar chart to complex renders of geographic spaces. Let's start by talking about things where you need only one point:
svg.append('circle') .attr('cx', 350) .attr('cy', 250) .attr('r', 100) .attr('fill', 'green') .attr('fill-opacity', 0.5) .attr('stroke', 'steelblue') .attr('stroke-width', 2);
A circle is defined by a central point (cx, cy) and a radius r. In this instance, we get a green circle with a steel blue border:
Mathematically speaking, a circle is just a special form of ellipse. ...
