Get the mouse direction while left click is pressed

How to get the mouse direction while left click is pressed?

 private var v3Pos : Vector3;
 private var threshold = 9;
 
 function OnMouseDown() {
     v3Pos = Input.mousePosition;
 }
 
 function OnMouseDrag() {
     var v3 = Input.mousePosition - v3Pos;
     v3.Normalize();
     var f = Vector3.Dot(v3, Vector3.up);
     if (Vector3.Distance(v3Pos, Input.mousePosition) < threshold) {
         Debug.Log("No movement");
         return;
     }
 
     if (f >= 0.5) {
        Debug.Log("Up");
     }
     else if (f <= -0.5) {
         Debug.Log("Down");
     }
     else {
         f = Vector3.Dot(v3, Vector3.right);
         if (f >= 0.5) {
             Debug.Log("Right");
         }
         else {
                 Debug.Log("Left");
         }
     }
    // v3Pos = Input.mousePosition;
 }
 
http://answers.unity3d.com/questions/452018/how-to-get-the-mouse-direction-while-left-click-is.ht
 }