def predict(self, input_data, path=None, missing_strategy=LAST_PREDICTION):
"""Makes a prediction based on a number of field values.
The input fields must be keyed by Id. There are two possible
strategies to predict when the value for the splitting field
is missing:
0 - LAST_PREDICTION: the last issued prediction is returned.
1 - PROPORTIONAL: as we cannot choose between the two branches
in the tree that stem from this split, we consider both. The
algorithm goes on until the final leaves are reached and
all their predictions are used to decide the final prediction.
"""
if path is None:
path = []
if missing_strategy == PROPORTIONAL:
(final_distribution, d_min, d_max, last_node, population,
parent_node) = self.predict_proportional(input_data, path=path)
if self.regression:
# singular case:
# when the prediction is the one given in a 1-instance node
if len(final_distribution.items()) == 1:
prediction, instances = final_distribution.items()[0]
if instances == 1:
return Prediction(
last_node.output,
path,
last_node.confidence,
distribution=(last_node.distribution if not \
self.weighted else \
last_node.weighted_distribution),
count=instances,
median=last_node.median,
distribution_unit=last_node.distribution_unit,
children=last_node.children,
d_min=last_node.min,
d_max=last_node.max)
# when there's more instances, sort elements by their mean
distribution = [
list(element)
for element in sorted(final_distribution.items(),
key=lambda x: x[0])
]
distribution_unit = ('bins' if len(distribution) > BINS_LIMIT
else 'counts')
distribution = merge_bins(distribution, BINS_LIMIT)
total_instances = sum(
[instances for _, instances in distribution])
if len(distribution) == 1:
# where there's only one bin, there will be no error, but
# we use a correction derived from the parent's error
prediction = distribution[0][0]
if total_instances < 2:
total_instances = 1
try:
# some strange models can have nodes with no confidence
confidence = round(
parent_node.confidence /
math.sqrt(total_instances), PRECISION)
except AttributeError:
confidence = None
else:
prediction = mean(distribution)
confidence = round(
regression_error(
unbiased_sample_variance(distribution, prediction),
total_instances), PRECISION)
return Prediction(prediction,
path,
confidence,
distribution=distribution,
count=total_instances,
median=dist_median(distribution,
total_instances),
distribution_unit=distribution_unit,
children=last_node.children,
d_min=d_min,
d_max=d_max)
else:
distribution = [
list(element)
for element in sorted(final_distribution.items(),
key=lambda x: (-x[1], x[0]))
]
return Prediction(distribution[0][0],
path,
ws_confidence(distribution[0][0],
final_distribution,
ws_n=population),
distribution=distribution,
count=population,
median=None,
distribution_unit='categorical',
children=last_node.children)
else:
if self.children:
for child in self.children:
if child.predicate.apply(input_data, self.fields):
path.append(child.predicate.to_rule(self.fields))
return child.predict(input_data, path=path)
if self.weighted:
output_distribution = self.weighted_distribution
output_unit = self.weighted_distribution_unit
else:
output_distribution = self.distribution
output_unit = self.distribution_unit
return Prediction(
self.output,
path,
self.confidence,
distribution=output_distribution,
count=get_instances(output_distribution),
median=None if not self.regression else self.median,
distribution_unit=output_unit,
children=self.children,
d_min=None if not self.regression else self.min,
d_max=None if not self.regression else self.max)
def predict(self, input_data, path=None, missing_strategy=LAST_PREDICTION):
"""Makes a prediction based on a number of field values.
The input fields must be keyed by Id. There are two possible
strategies to predict when the value for the splitting field
is missing:
0 - LAST_PREDICTION: the last issued prediction is returned.
1 - PROPORTIONAL: as we cannot choose between the two branches
in the tree that stem from this split, we consider both. The
algorithm goes on until the final leaves are reached and
all their predictions are used to decide the final prediction.
"""
if path is None:
path = []
if missing_strategy == PROPORTIONAL:
(final_distribution,
last_node) = self.predict_proportional(input_data, path=path)
if self.regression:
# singular case:
# when the prediction is the one given in a 1-instance node
if len(final_distribution.items()) == 1:
prediction, instances = final_distribution.items()[0]
if instances == 1:
return Prediction(
last_node.output,
path,
last_node.confidence,
distribution=last_node.distribution,
count=instances,
median=last_node.median,
distribution_unit=last_node.distribution_unit,
children=last_node.children)
# when there's more instances, sort elements by their mean
distribution = [list(element) for element in
sorted(final_distribution.items(),
key=lambda x: x[0])]
distribution_unit = ('bins' if len(distribution) > BINS_LIMIT
else 'counts')
distribution = merge_bins(distribution, BINS_LIMIT)
total_instances = sum([instances
for _, instances in distribution])
prediction = mean(distribution)
confidence = regression_error(
unbiased_sample_variance(distribution, prediction),
total_instances)
return Prediction(
prediction,
path,
confidence,
distribution=distribution,
count=total_instances,
median=dist_median(distribution, total_instances),
distribution_unit=distribution_unit,
children=last_node.children)
else:
distribution = [list(element) for element in
sorted(final_distribution.items(),
key=lambda x: (-x[1], x[0]))]
return Prediction(
distribution[0][0],
path,
ws_confidence(distribution[0][0], final_distribution),
distribution=distribution,
count=get_instances(distribution),
median=None,
distribution_unit='categorical',
children=last_node.children)
else:
if self.children:
for child in self.children:
if child.predicate.apply(input_data, self.fields):
path.append(child.predicate.to_rule(self.fields))
return child.predict(input_data, path=path)
return Prediction(
self.output,
path,
self.confidence,
distribution=self.distribution,
count=get_instances(self.distribution),
median=None if not self.regression else self.median,
distribution_unit=self.distribution_unit,
children=self.children)
def regression_proportional_predict(tree, weighted, fields, input_data):
"""Proportional prediction for regressions
"""
offset = OFFSETS[str(weighted)]
(final_distribution, d_min, d_max, last_node, population,
parent_node, path) = proportional_predict( \
tree, offset, fields, input_data, path=None)
# singular case:
# when the prediction is the one given in a 1-instance node
if len(list(final_distribution.items())) == 1:
prediction, instances = list(final_distribution.items())[0]
if instances == 1:
return Prediction( \
last_node[offset["output"]],
path,
last_node[offset["confidence"]],
distribution=last_node[offset["distribution"]] \
if not weighted else \
last_node[offset["wdistribution"]],
count=instances,
median=last_node[offset["median"]],
distribution_unit=last_node[offset["distribution_unit"]],
children=[] if last_node[offset["children#"]] == 0 else \
last_node[offset["children"]],
d_min=last_node[offset["min"]],
d_max=last_node[offset["max"]])
# when there's more instances, sort elements by their mean
distribution = [
list(element) for element in sorted(list(final_distribution.items()),
key=lambda x: x[0])
]
distribution_unit = ('bins'
if len(distribution) > BINS_LIMIT else 'counts')
distribution = merge_bins(distribution, BINS_LIMIT)
total_instances = sum([instances for _, instances in distribution])
if len(distribution) == 1:
# where there's only one bin, there will be no error, but
# we use a correction derived from the parent's error
prediction = distribution[0][0]
if total_instances < 2:
total_instances = 1
try:
# some strange models can have nodes with no confidence
confidence = round(
parent_node[offset["confidence"]] / math.sqrt(total_instances),
PRECISION)
except AttributeError:
confidence = None
else:
prediction = mean(distribution)
# weighted trees use the unweighted population to
# compute the associated error
confidence = round(
regression_error(
unbiased_sample_variance(distribution, prediction),
population), PRECISION)
return Prediction( \
prediction,
path,
confidence,
distribution=distribution,
count=total_instances,
median=dist_median(distribution, total_instances),
distribution_unit=distribution_unit,
children=[] if last_node[offset["children#"]] == 0 else \
last_node[offset["children"]],
d_min=d_min,
d_max=d_max)
