code: def get_points_within_r(center_points, target_points, r):
      r
      tree = cKDTree(target_points)
      indices = tree.query_ball_point(center_points, r)
      return tree.data[indices].T
docs: r"""Get all target_points within a specified radius of a center point.
  
      All data must be in same coordinate system, or you will get undetermined results.
  
      Parameters
      ----------
      center_points: (X, Y) ndarray
          location from which to grab surrounding points within r
      target_points: (X, Y) ndarray
          points from which to return if they are within r of center_points
      r: integer
          search radius around center_points to grab target_points
  
      Returns
      -------
      matches: (X, Y) ndarray
          A list of points within r distance of, and in the same
          order as, center_points