class NaiveBayesRecommender(Recommender):
_count_tables = {}
_item_features = None
_nb_table = None
_min_float = np.power(2.0, -149)
def __init__(self, item_features=None, thresh=2.9, alpha=0.01, beta=0.01):
self._count_tables = {}
self._item_features = item_features
self.selector = UnratedItemCandidateSelector()
self._nb_table = NaiveBayesTable(thresh, alpha, beta)
self.ensure_minimum_score(alpha)
self.ensure_minimum_score(beta)
# TODO: HOMEWORK 4
def fit(self, ratings, *args, **kwargs):
# Must fit the selector
self.selector.fit(ratings)
self._nb_table.reset()
# For each rating
# Get associated item features
# Update NBTable
for index, row in ratings.iterrows():
user, rating, item = row['user'], row['rating'], row['item']
features = self.get_features_list(item)
self._nb_table.process_rating(user, rating, features)
# TODO: HOMEWORK 4
# Should return ordered data frame with items and score
def recommend(self, user, n=None, candidates=None, ratings=None):
# n is None or zero, return DataFrame with an empty item column
if n is None or n == 0:
return pd.DataFrame({'item': []})
if candidates is None:
candidates = self.selector.candidates(user, ratings)
# Initialize scores
scores = []
# for each candidate
for candidate in candidates:
# Score the candidate for the user
score = self.score_item(user, candidate)
# Build list of candidate, score pairs
lists = [candidate, score]
scores.append(lists)
# Turn result into data frame
scores = pd.DataFrame(scores, columns=['item', 'score'])
# Retain n largest scoring rows (nlargest)
scores = scores.nlargest(n, 'score')
# Sort by score (sort_values)
scores = scores.sort_values(by='score', ascending=False)
# return data frame
return scores
# TODO: HOMEWORK 4
# Helper function to return a list of features for an item from features data frame
def get_features_list(self, item):
if item not in self._count_tables:
self._count_tables[item] = self._item_features[
self._item_features.item == item]['feature']
return self._count_tables[item]
# TODO: HOMEWORK 4
def score_item(self, user, item):
# get the features
# initialize the liked and nliked scores with the base probability
features = self.get_features_list(item)
liked_scores = self._nb_table.user_prob(user, True)
nliked_scores = self._nb_table.user_prob(user, False)
# for each feature
# update scores by multiplying with conditional probability
for feature in features:
liked_scores *= self._nb_table.user_feature_prob(
user, feature, True)
nliked_scores *= self._nb_table.user_feature_prob(
user, feature, False)
# Handle the case when scores go to zero.
liked_scores = self.ensure_minimum_score(liked_scores)
nliked_scores = self.ensure_minimum_score(nliked_scores)
# Compute log-likelihood
log_likelihood = np.log(liked_scores) - np.log(nliked_scores)
# Handle zero again
log_likelihood = self.ensure_minimum_score(log_likelihood)
# Return result
return log_likelihood
# DO NOT ALTER
def get_params(self, deep=True):
return {
'item_features': self._item_features,
'thresh': self._nb_table.thresh,
'alpha': self._nb_table.alpha,
'beta': self._nb_table.beta
}
# DO NOT ALTER
def ensure_minimum_score(self, val):
if val == 0.0:
return self._min_float
else:
return val
class WeightedHybrid(Predictor):
"""
"""
# HOMEWORK 3 TODO: Follow the constructor for Fallback, which can be found at
# https: // github.com / lenskit / lkpy / blob / master / lenskit / algorithms / basic.py
# Note that you will need to
# -- Check for agreement between the set of weights and the number of algorithms supplied.
# -- You should clone the algorithms with hwk3_util.my_clone() and store the cloned version.
# -- You should normalize the weights so they sum to 1.
# -- Keep the line that set the `selector` function.
algorithms = []
weights = []
def __init__(self, algorithms, weights):
"""
Args:
algorithms: a list of component algorithms. Each one will be trained.
weights: weights for each component to combine predictions.
"""
# HWK 3: Code here
self.algorithms = algorithms
self.weights = weights
self.selector = UnratedItemCandidateSelector()
list3 = []
for i in self.weights:
a = (i / sum(self.weights)) * 1
list3.append(a)
self.weights = list3
def clone(self):
return WeightedHybrid(self.algorithms, self.weights)
# HOMEWORK 3 TODO: Complete this implementation
# Will be similar to Fallback. Must also call self.selector.fit()
def fit(self, ratings, *args, **kwargs):
self.selector.fit(ratings)
# HWK 3: Code here
for algo in self.algorithms:
algo.fit(ratings, *args, **kwargs)
return self
def candidates(self, user, ratings):
return self.selector.candidates(user, ratings)
# HOMEWORK 3 TODO: Complete this implementation
# Computes the weighted average of the predictions from the component algorithms
def predict_for_user(self, user, items, ratings=None):
preds = None
predall = []
# HWK 3: Code here
#preds = None
for algo in self.algorithms:
#_logger.debug('predicting for %d items for user %s', len(remaining), user)
aps = algo.predict_for_user(user, items, ratings=ratings)
predall.append(aps)
preds = predall[0] * self.weights[0] + predall[1] * self.weights[1]
return preds
def __str__(self):
return 'Weighted([{}])'.format(', '.join(self.algorithms))
class WeightedHybrid(Predictor):
"""
"""
# HOMEWORK 3 TODO: Follow the constructor for Fallback, which can be found at
# https: // github.com / lenskit / lkpy / blob / master / lenskit / algorithms / basic.py
# Note that you will need to
# -- Check for agreement between the set of weights and the number of algorithms supplied.
# -- You should clone the algorithms with hwk3_util.my_clone() and store the cloned version.
# -- You should normalize the weights so they sum to 1.
# -- Keep the line that set the `selector` function.
algorithms = []
weights = []
def __init__(self, algorithms, weights):
"""
Args:
algorithms: a list of component algorithms. Each one will be trained.
weights: weights for each component to combine predictions.
"""
# HWK 3: Code here
if len(algorithms) != len(weights):
raise Exception(
'general exceptions not caught by specific handling')
self.algorithms = [my_clone(algo) for algo in algorithms]
self.weights = [my_clone(weight / sum(weights)) for weight in weights]
self.selector = UnratedItemCandidateSelector()
def clone(self):
return WeightedHybrid(self.algorithms, self.weights)
# HOMEWORK 3 TODO: Complete this implementation
# Will be similar to Fallback. Must also call self.selector.fit()
def fit(self, ratings, *args, **kwargs):
# HWK 3: Code here
for algo in self.algorithms:
algo.fit(ratings)
self.selector.fit(ratings)
return self
def candidates(self, user, ratings):
return self.selector.candidates(user, ratings)
# HOMEWORK 3 TODO: Complete this implementation
# Computes the weighted average of the predictions from the component algorithms
def predict_for_user(self, user, items, ratings=None):
preds = np.zeros_like(items.shape[0])
# HWK 3: Code here
for i in range(len(self.algorithms)):
algo_pred = self.algorithms[i].predict_for_user(user,
items,
ratings=ratings)
preds = preds + self.weights[i] * algo_pred
return preds
def __str__(self):
return 'Weighted([{}])'.format(', '.join(self.algorithms))
class NaiveBayesRecommender(Recommender):
_count_tables = {}
_item_features = None
_nb_table = None
_min_float = np.power(2.0, -149)
def __init__(self, item_features=None, thresh=2.9, alpha=0.01, beta=0.01):
self._item_features = item_features
self.selector = UnratedItemCandidateSelector()
self._nb_table = NaiveBayesTable(thresh, alpha, beta)
# TODO: HOMEWORK 4
def fit(self, ratings, *args, **kwargs):
# Must fit the selector
self.selector.fit(ratings)
self._nb_table.reset()
self._item_features.columns = ['item', 'feature']
# For each rating
for indexR, rowR in ratings.iterrows():
user = rowR['user']
item = rowR['item']
rating = rowR['rating']
# print("processing: ", user)
# Get associated item features
feature = self.get_features_list(item)
self._nb_table.process_rating(user, rating, feature)
# TODO: HOMEWORK 4
# Should return ordered data frame with items and score
def recommend(self, user, n=None, candidates=None, ratings=None):
# n is None or zero, return DataFrame with an empty item column
if n is None or n == 0:
return pd.DataFrame({'item': []})
if candidates is None:
candidates = self.selector.candidates(user, ratings)
# Initialize scores
scores = []
# for each candidate
for candidate in candidates:
scores.append(self.score_item(user, candidate))
# Score the candidate for the user
# Build list of candidate, score pairs
# Turn result into data frame
data = {'item': candidates, 'score': scores}
df = pd.DataFrame(data, columns=['item', 'score'])
# Retain n largest scoring rows (nlargest)
df = df.nlargest(n, 'score')
# Sort by score (sort_values)
df = df.sort_values(by=['score'], ascending=False)
# return data frame
return df
# TODO: HOMEWORK 4
# Helper function to return a list of features for an item from features data frame
def get_features_list(self, item):
features_list = []
for indexF, rowF in self._item_features.loc[self._item_features['item']
== item].iterrows():
features_list.append(rowF['feature'])
return features_list
# TODO: HOMEWORK 4
def score_item(self, user, item):
# get the features
features = self.get_features_list(item)
# initialize the liked and nliked scores with the base probability
baseP = self._nb_table.user_prob(user, True)
baseNP = self._nb_table.user_prob(user, False)
likeP = 1
nlikeP = 1
# for each feature
for feature in features:
likeP = likeP * self._nb_table.user_feature_prob(
user, feature, True)
nlikeP = nlikeP * self._nb_table.user_feature_prob(
user, feature, False)
# update scores by multiplying with conditional probability
likeP = likeP * baseP
nlikeP = nlikeP * baseNP
try:
ratio = likeP / nlikeP
except ZeroDivisionError:
# Handle the case when scores go to zero.
return 0
# Compute log-likelihood
try:
LL = math.log(ratio, math.e)
except ValueError:
# Handle zero again
return 0
# Return result
return LL
# DO NOT ALTER
def get_params(self, deep=True):
return {
'item_features': self._item_features,
'thresh': self._nb_table.thresh,
'alpha': self._nb_table.alpha,
'beta': self._nb_table.beta
}
# DO NOT ALTER
def ensure_minimum_score(self, val):
if val == 0.0:
return self._min_float
else:
return val
class WeightedHybrid(Predictor):
"""
"""
# HOMEWORK 3 TODO: Follow the constructor for Fallback, which can be found at
# https: // github.com / lenskit / lkpy / blob / master / lenskit / algorithms / basic.py
# Note that you will need to
# -- Check for agreement between the set of weights and the number of algorithms supplied.
# -- You should clone the algorithms with hwk3_util.my_clone() and store the cloned version.
# -- You should normalize the weights so they sum to 1.
# -- Keep the line that set the `selector` function.
algorithms = []
weights = []
def __init__(self, algorithms, weights):
"""
Args:
algorithms: a list of component algorithms. Each one will be trained.
weights: weights for each component to combine predictions.
"""
# HWK 3: Code here
# for algo in algorithms:
# self.algorithms.append(algo)
self.algorithms = algorithms
self.weights = []
w_sum = sum(weights)
for i in range(0, len(weights)):
self.weights.append(weights[i] / w_sum)
self.selector = UnratedItemCandidateSelector()
def clone(self):
return WeightedHybrid(self.algorithms, self.weights)
# HOMEWORK 3 TODO: Complete this implementation
# Will be similar to Fallback. Must also call self.selector.fit()
def fit(self, ratings, *args, **kwargs):
# HWK 3: Code here
for algo in self.algorithms:
# print(algo)
algo.fit(ratings, *args, **kwargs)
return self
def candidates(self, user, ratings):
return self.selector.candidates(user, ratings)
# HOMEWORK 3 TODO: Complete this implementation
# Computes the weighted average of the predictions from the component algorithms
def predict_for_user(self, user, items, ratings=None):
preds = None
# HWK 3: Code here
index = 0
for algo in self.algorithms:
# print(algo)
aps = algo.predict_for_user(user, items, ratings=ratings)
aps = aps[aps.notna()]
if preds is None:
preds = aps * self.weights[index]
else:
preds = preds + aps * self.weights[index]
index = index + 1
return preds
def __str__(self):
return 'Weighted([{}])'.format(', '.join(self.algorithms))