rotate_points.py

def rotate_points(x, y, x_axis_index, y_axis_index):
  num_points = len(x)
  x_rotated = []
  y_rotated = []
  x_axis_angle = math.atan2(y[x_axis_index], x[x_axis_index])
  y_axis_angle = math.atan2(y[y_axis_index], x[y_axis_index])
  if math.sin(y_axis_angle - x_axis_angle) < 0:
    flip_y = -1.0
  else:
    flip_y = 1.0
  for i in range(num_points):
    theta = math.atan2(y[i], x[i])
    radius = math.hypot(x[i], y[i])
    theta_rotated = theta - x_axis_angle
    x_rotated.append(radius*math.cos(theta_rotated))
    y_rotated.append(radius*math.sin(theta_rotated)*flip_y)
  return(x_rotated, y_rotated)