.. _rank-bm25-getting-started:

Getting started
===============


Installation
------------

Rank-BM25 is included in the full ``scikit-plots`` distribution. It is also
shipped as the project-maintained partial distribution
``scikit-plots-rank-bm25``::

   python -m pip install scikit-plots-rank-bm25

Do not install the partial distribution alongside the full distribution in the
same environment: both own ``scikitplot.rank_bm25`` files. See
:doc:`../../affiliated/index` for the repository's partial-distribution model.

.. code-block:: python

   from scikitplot.rank_bm25 import BM25Okapi

   texts = [
       "hello there good man",
       "it is quite windy in london",
       "how is the weather today",
   ]
   corpus = [text.lower().split() for text in texts]
   ids = ["greeting", "london-weather", "question"]

   index = BM25Okapi(corpus, doc_ids=ids)
   hits = index.get_top_ids("windy london".split(), n=2)

``get_top_ids`` is the preferred retrieval surface when results need stable
identity. An out-of-vocabulary query returns no sparse candidates instead of
inventing an arbitrary zero-score ordering.