Basic algorithms

These are basic algorithms that do not do much work but that are still useful for comparing accuracies.

class surprise.prediction_algorithms.random_pred.NormalPredictor

Bases: surprise.prediction_algorithms.algo_base.AlgoBase

Algorithm predicting a random rating based on the distribution of the training set, which is assumed to be normal.

The prediction \(\hat{r}_{ui}\) is generated from a normal distribution \(\mathcal{N}(\hat{\mu}, \hat{\sigma}^2)\) where \(\hat{\mu}\) and \(\hat{\sigma}\) are estimated from the training data using Maximum Likelihood Estimation:

\[\begin{split}\hat{\mu} &= \frac{1}{|R_{train}|} \sum_{r_{ui} \in R_{train}} r_{ui}\\\\ \hat{\sigma} &= \sqrt{\sum_{r_{ui} \in R_{train}} \frac{(r_{ui} - \hat{\mu})^2}{|R_{train}|}}\end{split}\]
class surprise.prediction_algorithms.baseline_only.BaselineOnly(bsl_options={}, verbose=True)

Bases: surprise.prediction_algorithms.algo_base.AlgoBase

Algorithm predicting the baseline estimate for given user and item.

\(\hat{r}_{ui} = b_{ui} = \mu + b_u + b_i\)

If user \(u\) is unknown, then the bias \(b_u\) is assumed to be zero. The same applies for item \(i\) with \(b_i\).

See section 2.1 of [Kor10] for details.

  • bsl_options (dict) – A dictionary of options for the baseline estimates computation. See Baselines estimates configuration for accepted options.
  • verbose (bool) – Whether to print trace messages of bias estimation, similarity, etc. Default is True.