This works with the sketches from this data visualization tutorial.

Scaling positions to the canvas can also make it easy to view geographical data. Here the data points representing longitude and latitude are scaled to the size of the canvas.

This sketch uses a second canvas (called with createGraphics()) to load all of the data points as a background. The highlighting is done in the draw loop. Mouse over to see arrival airports and departure airports highlighted. Every time the mouse is moved, redraw() is called, and new points are highlighted with the new position of the mouse.