Example for ternary plotting (https://en.wikipedia.org/wiki/Ternary_plot) like in moovellab's mobility space explorer

ternaryplot.js

console.log();
console.log('Examples');
console.log();
console.log('- All Bike (dot bottom right)');
console.log('   ', mobilityTriangle(1123, 0, 0) );
console.log();
console.log('- All Car (dot top)');
console.log('   ', mobilityTriangle(0, 124, 0) );
console.log();
console.log('- All Rail (dot bottom left)');
console.log('   ', mobilityTriangle(0, 0, 647) );
console.log();
console.log('- Balanced (dot in center)');
console.log('   ', mobilityTriangle(25, 25, 25) );
console.log();
console.log('- More realistic example');
console.log('   ', mobilityTriangle(15, 231, 45) );

function mobilityTriangle(bike, car, rail) {
    return coordinateInTriangle(bike, car, rail);
}

function coordinateInTriangle(a, b, c, edgeLength) {
    edgeLength = edgeLength || 1;
    // See https://en.wikipedia.org/wiki/Ternary_plot
    var sum = a + b + c;
    var fractionA = a / sum;
    var fractionB = b / sum;
    var fractionC = c / sum;

    var y = fractionB * Math.sin(toRadians(60));
    var x = fractionA + y * cot(toRadians(60));
    return {
        "x": x * edgeLength,
        "y": y * edgeLength
    }
}

function toRadians(degrees) {
    return degrees * Math.PI / 180;
}

function toDegrees(radians) {
    return radians / Math.PI * 180;
}

function cot(x) {
    return 1 / Math.tan(x);
}