//change angleVel to see different result

//the higher the angular velocity, the shorter the period

let angleVel = 0.2;

​

function setup() {

  createCanvas(560,390);

  background(220);

  stroke(63,63,147);

  strokeWeight(2);

  noFill();

  //use beginShape() and endShape() to connect the points with a line

  beginShape();

  for (let x = 0; x <= width; x += 5) {

    //calculate y location according to amplitude and sine of the angle

    //we use map() function instead to calculate the vertical location 

    let y = map(sin(angle), -1, 1, 0, height);

    //within beginShape(), we call vertex() to set all the vertices of our shape

    vertex(x, y);

    //increment the angle according to angular velocity

    angle += angleVel;

  }

  endShape();

}