LKPY’s batch routines and utility support for managing algorithms expect algorithms to implement consistent interfaces. This page describes those interfaces.
The interfaces are realized as abstract base classes with the Python
Implementations must be registered with their interfaces, either by subclassing the interface
or by calling
Algorithms follow the SciKit fit-predict paradigm for estimators, except they know natively how to work with Pandas objects.
Algorithm interface defines common methods.
Base class for LensKit algorithms. These algorithms follow the SciKit design pattern for estimators.
fit(ratings, *args, **kwargs)¶
Train a model using the specified ratings (or similar) data.
- ratings (pandas.DataFrame) – The ratings data.
- args – Additional training data the algorithm may require.
- kwargs – Additional training data the algorithm may require.
The algorithm object.
Get the parameters for this algorithm (as in scikit-learn). Algorithm parameters should match constructor argument names.
The default implementation returns all attributes that match a constructor parameter name. It should be compatible with
scikit.base.BaseEstimator.get_params()method so that LensKit alogrithms can be cloned with
scikit.base.clone()as well as
Returns: the algorithm parameters. Return type: dict
Recommender interface provides an interface to generating recommendations. Not
all algorithms implement it; call
Recommender.adapt() on an algorithm to get a recommender
for any algorithm that at least implements
Predictor. For example:
pred = Bias(damping=5) rec = Recommender.adapt(pred)
We are rethinking the ergonomics of this interface, and it may change in LensKit 0.6. We expect
keep compatibility in the
lenskit.batch.recommend() API, though.
Recommends lists of items for users.
Ensure that an algorithm is a
Recommender. If it is not a recommender, it is wrapped in a
lenskit.basic.TopNwith a default candidate selector.
Parameters: algo (Predictor) – the underlying rating predictor.
recommend(user, n=None, candidates=None, ratings=None)¶
Compute recommendations for a user.
- user – the user ID
- n (int) – the number of recommendations to produce (
- candidates (array-like) – The set of valid candidate items; if
None, a default set will be used. For many algorithms, this is their
- ratings (pandas.Series) – the user’s ratings (indexed by item id); if provided, they may be used to override or augment the model’s notion of a user’s preferences.
a frame with an
itemcolumn; if the recommender also produces scores, they will be in a
Some recommenders use a candidate selector to identify possible items to recommend. These are also treated as algorithms, mainly so that they can memorize users’ prior ratings to exclude them from recommendation.
Select candidates for recommendation for a user, possibly with some additional ratings.
Select candidates for the user.
Predicts user ratings of items. Predictions are really estimates of the user’s like or dislike, and the
Predictorinterface makes no guarantees about their scale or granularity.
Compute predictions for user-item pairs. This method is designed to be compatible with the general SciKit paradigm; applications typically want to use
The predicted scores for each user-item pair.
predict_for_user(user, items, ratings=None)¶
Compute predictions for a user and items.
- user – the user ID
- items (array-like) – the items to predict
scores for the items, indexed by item id.