node-d3-contour 1.3.2-4 (amd64 binary) in ubuntu hirsute

 squares to a rectangular array.
 .
 Computes contour polygons by applying marching squares to a
 rectangular array of numeric values.
 .
 Contour polygons are GeoJSON, you can transform and display
 them using standard tools.
 .
 Contour plots can also visualize continuous functions by sampling.
 .
 Contours can also show the estimated density of point clouds,
 which is especially useful to avoid overplotting in large
 datasets. This library implements fast two-dimensional kernel
 density estimation.
 .
 Node.js is an event-based server-side JavaScript engine.