"""
This is the implementation of the Mean Squared Error metric.
It proceeds from a system-wise computation.
"""
__version__ = '0.3.1'
__author__ = 'Vito Walter Anelli, Claudio Pomo'
__email__ = 'vitowalter.anelli@poliba.it, claudio.pomo@poliba.it'
from elliot.evaluation.metrics.base_metric import BaseMetric
from elliot.utils import logging
[docs]class MSE(BaseMetric):
r"""
Mean Squared Error
This class represents the implementation of the Mean Squared Error recommendation metric.
For further details, please refer to the `link <https://en.wikipedia.org/wiki/Mean_squared_error>`_
.. math::
\mathrm{MSE} = \frac{1}{|{T}|} \sum_{(u, i) \in {T}}(\hat{r}_{u i}-r_{u i})^{2}
:math:`T` is the test set, :math:`\hat{r}_{u i}` is the score predicted by the model
:math:`r_{u i}` the actual score of the test set.
To compute the metric, add it to the config file adopting the following pattern:
.. code:: yaml
simple_metrics: [MSE]
"""
def __init__(self, recommendations, config, params, eval_objects):
"""
Constructor
:param recommendations: list of recommendations in the form {user: [(item1,value1),...]}
:param config: SimpleNameSpace that represents the configuration of the experiment
:param params: Parameters of the model
:param eval_objects: list of objects that may be useful for the computation of the different metrics
"""
super().__init__(recommendations, config, params, eval_objects)
self._relevance = self._evaluation_objects.relevance.binary_relevance
self._total_relevant_items = sum([len(self._relevance.get_user_rel(u)) for u, _ in self._recommendations.items()])
self._test = self._evaluation_objects.relevance.get_test()
[docs] @staticmethod
def name():
"""
Metric Name Getter
:return: returns the public name of the metric
"""
return "MSE"
@staticmethod
def __user_MSE(user_recommendations, user_test, user_relevant_items):
"""
Per User computation for Mean Squared Error
:param user_recommendations: list of user recommendation in the form [(item1,value1),...]
:param cutoff: numerical threshold to limit the recommendation list
:param user_relevant_items: list of user relevant items in the form [item1,...]
:return: the value of the Precision metric for the specific user
"""
return sum([(v - user_test[i])**2 for i, v in user_recommendations if i in user_relevant_items])
[docs] def eval(self):
"""
Evaluation function
:return: the overall averaged value of Mean Squared Error
"""
return sum(
[MSE.__user_MSE(u_r, self._test[u], self._relevance.get_user_rel(u))
for u, u_r in self._recommendations.items() if len(self._relevance.get_user_rel(u))]
) / self._total_relevant_items
[docs] def eval_user_metric(self):
"""
Evaluation function
:return: the overall averaged value of Mean Squared Error per user
"""
return {u: MSE.__user_MSE(u_r, self._test[u], self._relevance.get_user_rel(u))/len(self._relevance.get_user_rel(u))
for u, u_r in self._recommendations.items() if len(self._relevance.get_user_rel(u))}
[docs] @staticmethod
def needs_full_recommendations():
_logger = logging.get_logger("Evaluator")
_logger.warn("WARNING: Mean Absolute Error metric requires full length recommendations")
return True