lenskit.metrics.ranking.RankWeight
==================================

.. py:class:: lenskit.metrics.ranking.RankWeight
   :canonical: lenskit.metrics.ranking._weighting.RankWeight

   Bases: :py:obj:`abc.ABC`


   Base class for rank weighting models.

   This returns *multiplicative* weights, such that scores should be multiplied
   by the weights in order to produce weighted scores.

   :Stability: caller


   .. py:method:: weight(ranks)
      :abstractmethod:


      Compute the discount for the specified ranks.

      Ranks must start with 1.



   .. py:method:: log_weight(ranks)

      Compute the (natural) log of the discount for the specified ranks.

      Ranks must start with 1.



   .. py:method:: series_sum()

      Get the sum of the infinite series of this discount function, if known.
      Some metrics (e.g. :func:`~lenskit.metrics.RBP`) will use this to
      normalize their measurements.