code: function getDirection(touch1, touch2) {
        var x = Math.abs(touch1.pageX - touch2.pageX),
        y = Math.abs(touch1.pageY - touch2.pageY);
  
        if(x >= y) {
          return touch1.pageX - touch2.pageX > 0 ? ionic.Gestures.DIRECTION_LEFT : ionic.Gestures.DIRECTION_RIGHT;
        }
        else {
          return touch1.pageY - touch2.pageY > 0 ? ionic.Gestures.DIRECTION_UP : ionic.Gestures.DIRECTION_DOWN;
        }
      }
docs: angle to direction define
  @param   {Touch}     touch1
  @param   {Touch}     touch2
  @returns {String}    direction constant, like ionic.Gestures.DIRECTION_LEFT