def lyap_r_len(**kwargs):
  """
  Helper function that calculates the minimum number of data points required
  to use lyap_r.

  Note that none of the required parameters may be set to None.

  Kwargs:
    kwargs(dict):
      arguments used for lyap_r (required: emb_dim, lag, trajectory_len and
      min_tsep)

  Returns:
    minimum number of data points required to call lyap_r with the given
    parameters
  """
  # minimum length required to find single orbit vector
  min_len = (kwargs['emb_dim'] - 1) * kwargs['lag'] + 1
  # we need trajectory_len orbit vectors to follow a complete trajectory
  min_len += kwargs['trajectory_len'] - 1
  # we need min_tsep * 2 + 1 orbit vectors to find neighbors for each
  min_len += kwargs['min_tsep'] * 2 + 1
  return min_len