Compute contour polygons

 This module 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.