Spike map

[mbostock]

Some way of generating this type of map would be nice:

https://observablehq.com/@d3/spike-map

[Fil]

Should we add the spike symbol to Plot? It needs a base width parameter, so it can't really be a named symbol.
https://observablehq.com/@observablehq/plot-spike-map

[Fil]

Using a dot mark with a custom symbol (as I do in this notebook) makes an incorrect use of the r scale. The spike would be better defined by a length scale. A good approach might be to make the vector mark’s path adjustable with a {draw} object, in

plot/src/marks/vector.js

Line 63 in 2b318ac

.attr("d", (i) => {

, which would support angle and length.