svg / d3.js rounded corners on one side of a rectangle

Expanding on @robert-longson’s answer, you can use SVG’s elliptical arc commands to make the corners, in conjunction with lineto commands for the straight edges. These are used with path elements. Here’s one possible implementation:

// Returns path data for a rectangle with rounded right corners.
// The top-left corner is ⟨x,y⟩.
function rightRoundedRect(x, y, width, height, radius) {
  return "M" + x + "," + y
       + "h" + (width - radius)
       + "a" + radius + "," + radius + " 0 0 1 " + radius + "," + radius
       + "v" + (height - 2 * radius)
       + "a" + radius + "," + radius + " 0 0 1 " + -radius + "," + radius
       + "h" + (radius - width)
       + "z";
}

You can then call this function to compute the “d” attribute. For example:

rects.enter().append("path")
    .attr("d", function(d) {
      return rightRoundedRect(x(0), y(d.name), x(d.value) - x(0), y.rangeBand(), 10);
    });

Live example:

• http://bl.ocks.org/3468167

Optional: If you like, you could refactor the rightRoundedRect function to make it configurable, rather than taking lots of arguments. This approach would be similar to D3’s built-in shape generators. For example, you might use a rect generator like so:

rects.enter().append("path")
    .attr("d", rightRoundedRect()
      .x(x(0))
      .y(function(d) { return y(d.name); })
      .width(function(d) { return x(d.value) - x(0); })
      .height(y.rangeBand())
      .radius(10));

For more details on that approach, see the configurable function tutorial.