calculate-relationships.js

// initial metrics
var initialRise = finger0.initial.y - finger1.initial.y;
var initialRun = finger0.initial.x - finger1.initial.x;
var initialTheta = Math.atan2(initialRise, initialRun);
var initialAngle = 180 - (initialTheta * 180 / Math.PI);
if (initialAngle < 0)
    initialAngle += 180;

// latest metrics
var latestRise = finger0.latest.y - finger1.latest.y;
var latestRun = finger0.latest.x - finger1.latest.x;
var latestTheta = Math.atan2(latestRise, latestRun);
var latestAngle = 180 - (latestTheta * 180 / Math.PI);
if (latestAngle < 0)
    latestAngle += 180;

// change in the angle between the two points over time
var deltaSweep = Math.abs(initialAngle - latestAngle);