Empty line segments not displayed in d3.svg.line.

[kraf]

I can't get a line chart to display single points. In SVG it get's rendered as a dot when I move the pen to a point and then do a line to with the same coordinates (at least with a linecap different than "butt"). I noticed that d3.svg.line just creates the moves of the pen. Is this intentional?
I provided an example: http://jsfiddle.net/ntdwa4dv/1/

[mbostock]

This is probably a bug (and I don’t think we’d need a new API to fix it). One simple fix is to patch this code in svg/line.js:

function segment() {
  segments.push("M", interpolate(projection(points), tension) || "z");
}

This causes d3.svg.line to use "z" for empty segments, producing a zero-length line, rather than a bare "M" command which draws nothing. This is probably the right fix, although perhaps not the optimal one.

But this fix would still require you to use stroke-linecap: round or stroke-linecap: square, and the dots would still be pretty small (dependent on the stroke-width). You might consider rendering each data point explicitly, say as circles on top of the line, so that you have more control over how they are displayed.

[jasondavies]

Sounds reasonable.

[mbostock]

A workaround for the time-being:

line.interpolate(function(points) { return points.length > 1 ? points.join("L") : points + "z"; });

[mbostock]

Fix staged in #2591 for 3.5.7.

[mbostock]

http://bl.ocks.org/mbostock/bbbe5171af94cc4b18c1