egg Chronology of Computer Languages 4

I couldn't resist re-visiting this after the Bank Holiday weekend.

After a bit more research, the type of diagram I'm actually looking for for COCL is a layered graph drawing, also known as a Sugiyama diagram. As suspected, it's a difficult problem to lay out these diagrams but there are some well-known heuristics. Placing a descendant at an x-position that is an average (mean, median, etc.) of its ancestors' x-positions helps reduce edge crossings. It also seems to organise the programming languages of COCL into related groups.

So I did a bit more fettling of the box-drawing version of the data-set and then produced a colourful SVG version based on that layout data. The only slight wrinkle was getting the arcs looking good when there isn't enough room for a full ninety-degree elbow. See the purple link between "Lisp" and "Logo" below:

I didn't animate the final SVG because it's just too expensive computationally and there's no scope for caching frames like I did with the canvas-based "waterfall" version.

The opacity of each connection is a function of the time in years between the appearance of the ancestor and the descendant. I'm not sure it's strictly meaningful, but it adds variety.