// Daniel Shiffman

// http://natureofcode.com

​

// An array to keep track of how often random numbers are picked

let randomCounts = [];

​

function setup() {

  createCanvas(640, 240);

  for (let i = 0; i < 20; i++) {

    randomCounts[i] = 0;

  }

}

​

function draw() {

  background(255);

​

  // Pick a random number and increase the count

  let index = int(acceptreject() * randomCounts.length);

  randomCounts[index]++;

​

  // Draw a rectangle to graph results

  stroke(0);

  strokeWeight(2);

  fill(127);

​

  let w = width / randomCounts.length;

​

  for (let x = 0; x < randomCounts.length; x++) {

    rect(x * w, height - randomCounts[x], w - 1, randomCounts[x]);

  }

}

​

// An algorithm for picking a random number based on monte carlo method

// Here probability is determined by formula y = x

function acceptreject() {

  // We do this “forever” until we find a qualifying random value.

  while (true) {

    // Pick a random value.

    let r1 = random(1);

    // Assign a probability.

    let probability = r1;

    // Pick a second random value.

    let r2 = random(1);

​

    //{!3} Does it qualify?  If so, we’re done!

    if (r2 < probability) {

      return r1;

    }

  }

}