Illustrates how to use Vladimir Agafonkin’s clever simpleheat JS library to overlay a heatmap of Hopper search destinations on a D3 map.
Just for fun we use a separate svg layer ‘under’ the canvas to display the map, although it’s easy enough to have D3 render direct to the canvas. The default canvas (and svg) ‘background’ is transparent so we can see through layers, making it easy to build up (say) an animated heatmap over a static map without continually redrawing the latter.
This was originally a gist hosted at bl.ocks.org, which seems dead now. This clone might still work.