void setup() {
  size(400, 400);
  translate(0, height/2);
  for (int a = 0; a < width; a++) {
    point(a, mySin(a));
  }
}

float mySin(float angle) {
  float amplitude =  100.; // height of curve
  float frequency = 3;     // how many cycles 
  float y = amplitude*sin(frequency*radians(angle)); 
  return y;
}