反正切函数返回怪异值

Question

In Processing, I'm trying to set a sprite's direction and momentum by clicking where to place it, and releasing the mouse to show what direction it should move in, with 0 degrees being directly upwards. However, the atan() function returns weird values, ranging from about 30 degrees to about 60. I've already made sure it's not a problem converting radians/degrees, and I still can't figure it out.

void mousePressed(){
  if (ballCount<limit){
    ballX[ballCount]=mouseX;
    ballY[ballCount]=mouseY;
    ball[ballCount]=true;
    ballSize[ballCount]=currentSize;
  }
}

void mouseReleased(){
  if (ballCount<limit){ //This next line is the one I'm having problems with
    ballDir[ballCount]=atan((ballX[ballCount]-mouseX)/(ballY[ballCount]-mouseY));
    println(degrees((ballDir[ballCount])));

    ballCount++;
  }
}

Answer 1

Never mind, I found the answer. A different method was running in draw() that would update the ballCount variable based on the amount of balls[] that were true, and so the ballCount variable would differ between mousePressed() and mouseReleased().