Learn more »
Push, build, and install
RubyGems
npm packages
Python packages
Maven artifacts
PHP packages
Go Modules
Bower components
Debian packages
RPM packages
NuGet packages
/ metrics / _regression.py
"""Metrics to assess performance on regression task
Functions named as ``*_score`` return a scalar value to maximize: the higher
the better
Function named as ``*_error`` or ``*_loss`` return a scalar value to minimize:
the lower the better
"""
# Authors: Alexandre Gramfort <alexandre.gramfort@inria.fr>
# Mathieu Blondel <mathieu@mblondel.org>
# Olivier Grisel <olivier.grisel@ensta.org>
# Arnaud Joly <a.joly@ulg.ac.be>
# Jochen Wersdorfer <jochen@wersdoerfer.de>
# Lars Buitinck
# Joel Nothman <joel.nothman@gmail.com>
# Karan Desai <karandesai281196@gmail.com>
# Noel Dawe <noel@dawe.me>
# Manoj Kumar <manojkumarsivaraj334@gmail.com>
# Michael Eickenberg <michael.eickenberg@gmail.com>
# Konstantin Shmelkov <konstantin.shmelkov@polytechnique.edu>
# Christian Lorentzen <lorentzen.ch@googlemail.com>
# License: BSD 3 clause
import numpy as np
from scipy.special import xlogy
import warnings
from ..utils.validation import (check_array, check_consistent_length,
_num_samples)
from ..utils.validation import column_or_1d
from ..exceptions import UndefinedMetricWarning
__ALL__ = [
"max_error",
"mean_absolute_error",
"mean_squared_error",
"mean_squared_log_error",
"median_absolute_error",
"r2_score",
"explained_variance_score",
"mean_tweedie_deviance",
"mean_poisson_deviance",
"mean_gamma_deviance",
]
def _check_reg_targets(y_true, y_pred, multioutput, dtype="numeric"):
"""Check that y_true and y_pred belong to the same regression task
Parameters
----------
y_true : array-like
y_pred : array-like
multioutput : array-like or string in ['raw_values', uniform_average',
'variance_weighted'] or None
None is accepted due to backward compatibility of r2_score().
Returns
-------
type_true : one of {'continuous', continuous-multioutput'}
The type of the true target data, as output by
'utils.multiclass.type_of_target'
y_true : array-like of shape (n_samples, n_outputs)
Ground truth (correct) target values.
y_pred : array-like of shape (n_samples, n_outputs)
Estimated target values.
multioutput : array-like of shape (n_outputs) or string in ['raw_values',
uniform_average', 'variance_weighted'] or None
Custom output weights if ``multioutput`` is array-like or
just the corresponding argument if ``multioutput`` is a
correct keyword.
dtype: str or list, default="numeric"
the dtype argument passed to check_array
"""
check_consistent_length(y_true, y_pred)
y_true = check_array(y_true, ensure_2d=False, dtype=dtype)
y_pred = check_array(y_pred, ensure_2d=False, dtype=dtype)
if y_true.ndim == 1:
y_true = y_true.reshape((-1, 1))
if y_pred.ndim == 1:
y_pred = y_pred.reshape((-1, 1))
if y_true.shape[1] != y_pred.shape[1]:
raise ValueError("y_true and y_pred have different number of output "
"({0}!={1})".format(y_true.shape[1], y_pred.shape[1]))
n_outputs = y_true.shape[1]
allowed_multioutput_str = ('raw_values', 'uniform_average',
'variance_weighted')
if isinstance(multioutput, str):
if multioutput not in allowed_multioutput_str:
raise ValueError("Allowed 'multioutput' string values are {}. "
"You provided multioutput={!r}".format(
allowed_multioutput_str,
multioutput))
elif multioutput is not None:
multioutput = check_array(multioutput, ensure_2d=False)
if n_outputs == 1:
raise ValueError("Custom weights are useful only in "
"multi-output cases.")
elif n_outputs != len(multioutput):
raise ValueError(("There must be equally many custom weights "
"(%d) as outputs (%d).") %
(len(multioutput), n_outputs))
y_type = 'continuous' if n_outputs == 1 else 'continuous-multioutput'
return y_type, y_true, y_pred, multioutput
def mean_absolute_error(y_true, y_pred,
sample_weight=None,
multioutput='uniform_average'):
"""Mean absolute error regression loss
Read more in the :ref:`User Guide <mean_absolute_error>`.
Parameters
----------
y_true : array-like of shape (n_samples,) or (n_samples, n_outputs)
Ground truth (correct) target values.
y_pred : array-like of shape (n_samples,) or (n_samples, n_outputs)
Estimated target values.
sample_weight : array-like of shape (n_samples,), optional
Sample weights.
multioutput : string in ['raw_values', 'uniform_average']
or array-like of shape (n_outputs)
Defines aggregating of multiple output values.
Array-like value defines weights used to average errors.
'raw_values' :
Returns a full set of errors in case of multioutput input.
'uniform_average' :
Errors of all outputs are averaged with uniform weight.
Returns
-------
loss : float or ndarray of floats
If multioutput is 'raw_values', then mean absolute error is returned
for each output separately.
If multioutput is 'uniform_average' or an ndarray of weights, then the
weighted average of all output errors is returned.
MAE output is non-negative floating point. The best value is 0.0.
Examples
--------
>>> from sklearn.metrics import mean_absolute_error
>>> y_true = [3, -0.5, 2, 7]
>>> y_pred = [2.5, 0.0, 2, 8]
>>> mean_absolute_error(y_true, y_pred)
0.5
>>> y_true = [[0.5, 1], [-1, 1], [7, -6]]
>>> y_pred = [[0, 2], [-1, 2], [8, -5]]
>>> mean_absolute_error(y_true, y_pred)
0.75
>>> mean_absolute_error(y_true, y_pred, multioutput='raw_values')
array([0.5, 1. ])
>>> mean_absolute_error(y_true, y_pred, multioutput=[0.3, 0.7])
0.85...
"""
y_type, y_true, y_pred, multioutput = _check_reg_targets(
y_true, y_pred, multioutput)
check_consistent_length(y_true, y_pred, sample_weight)
output_errors = np.average(np.abs(y_pred - y_true),
weights=sample_weight, axis=0)
if isinstance(multioutput, str):
if multioutput == 'raw_values':
return output_errors
elif multioutput == 'uniform_average':
# pass None as weights to np.average: uniform mean
multioutput = None
return np.average(output_errors, weights=multioutput)
def mean_squared_error(y_true, y_pred,
sample_weight=None,
multioutput='uniform_average', squared=True):
"""Mean squared error regression loss
Read more in the :ref:`User Guide <mean_squared_error>`.
Parameters
----------
y_true : array-like of shape (n_samples,) or (n_samples, n_outputs)
Ground truth (correct) target values.
y_pred : array-like of shape (n_samples,) or (n_samples, n_outputs)
Estimated target values.
sample_weight : array-like of shape (n_samples,), optional
Sample weights.
multioutput : string in ['raw_values', 'uniform_average']
or array-like of shape (n_outputs)
Defines aggregating of multiple output values.
Array-like value defines weights used to average errors.
'raw_values' :
Returns a full set of errors in case of multioutput input.
'uniform_average' :
Errors of all outputs are averaged with uniform weight.
squared : boolean value, optional (default = True)
If True returns MSE value, if False returns RMSE value.
Returns
-------
loss : float or ndarray of floats
A non-negative floating point value (the best value is 0.0), or an
array of floating point values, one for each individual target.
Examples
--------
>>> from sklearn.metrics import mean_squared_error
>>> y_true = [3, -0.5, 2, 7]
>>> y_pred = [2.5, 0.0, 2, 8]
>>> mean_squared_error(y_true, y_pred)
0.375
>>> y_true = [3, -0.5, 2, 7]
>>> y_pred = [2.5, 0.0, 2, 8]
>>> mean_squared_error(y_true, y_pred, squared=False)
0.612...
>>> y_true = [[0.5, 1],[-1, 1],[7, -6]]
>>> y_pred = [[0, 2],[-1, 2],[8, -5]]
>>> mean_squared_error(y_true, y_pred)
0.708...
>>> mean_squared_error(y_true, y_pred, multioutput='raw_values')
array([0.41666667, 1. ])
>>> mean_squared_error(y_true, y_pred, multioutput=[0.3, 0.7])
0.825...
"""
y_type, y_true, y_pred, multioutput = _check_reg_targets(
y_true, y_pred, multioutput)
check_consistent_length(y_true, y_pred, sample_weight)
output_errors = np.average((y_true - y_pred) ** 2, axis=0,
weights=sample_weight)
if isinstance(multioutput, str):
if multioutput == 'raw_values':
return output_errors
elif multioutput == 'uniform_average':
# pass None as weights to np.average: uniform mean
multioutput = None
mse = np.average(output_errors, weights=multioutput)
return mse if squared else np.sqrt(mse)
def mean_squared_log_error(y_true, y_pred,
sample_weight=None,
multioutput='uniform_average'):
"""Mean squared logarithmic error regression loss
Read more in the :ref:`User Guide <mean_squared_log_error>`.
Parameters
----------
y_true : array-like of shape (n_samples,) or (n_samples, n_outputs)
Ground truth (correct) target values.
y_pred : array-like of shape (n_samples,) or (n_samples, n_outputs)
Estimated target values.
sample_weight : array-like of shape (n_samples,), optional
Sample weights.
multioutput : string in ['raw_values', 'uniform_average'] \
or array-like of shape (n_outputs)
Defines aggregating of multiple output values.
Array-like value defines weights used to average errors.
'raw_values' :
Returns a full set of errors when the input is of multioutput
format.
'uniform_average' :
Errors of all outputs are averaged with uniform weight.
Returns
-------
loss : float or ndarray of floats
A non-negative floating point value (the best value is 0.0), or an
array of floating point values, one for each individual target.
Examples
--------
>>> from sklearn.metrics import mean_squared_log_error
>>> y_true = [3, 5, 2.5, 7]
>>> y_pred = [2.5, 5, 4, 8]
>>> mean_squared_log_error(y_true, y_pred)
0.039...
>>> y_true = [[0.5, 1], [1, 2], [7, 6]]
>>> y_pred = [[0.5, 2], [1, 2.5], [8, 8]]
>>> mean_squared_log_error(y_true, y_pred)
0.044...
>>> mean_squared_log_error(y_true, y_pred, multioutput='raw_values')
array([0.00462428, 0.08377444])
>>> mean_squared_log_error(y_true, y_pred, multioutput=[0.3, 0.7])
0.060...
"""
y_type, y_true, y_pred, multioutput = _check_reg_targets(
y_true, y_pred, multioutput)
check_consistent_length(y_true, y_pred, sample_weight)
if (y_true < 0).any() or (y_pred < 0).any():
raise ValueError("Mean Squared Logarithmic Error cannot be used when "
"targets contain negative values.")
return mean_squared_error(np.log1p(y_true), np.log1p(y_pred),
sample_weight, multioutput)
def median_absolute_error(y_true, y_pred, multioutput='uniform_average'):
"""Median absolute error regression loss
Median absolute error output is non-negative floating point. The best value
is 0.0. Read more in the :ref:`User Guide <median_absolute_error>`.
Parameters
----------
y_true : array-like of shape = (n_samples) or (n_samples, n_outputs)
Ground truth (correct) target values.
y_pred : array-like of shape = (n_samples) or (n_samples, n_outputs)
Estimated target values.
multioutput : {'raw_values', 'uniform_average'} or array-like of shape
(n_outputs,)
Defines aggregating of multiple output values. Array-like value defines
weights used to average errors.
'raw_values' :
Returns a full set of errors in case of multioutput input.
'uniform_average' :
Errors of all outputs are averaged with uniform weight.
Returns
-------
loss : float or ndarray of floats
If multioutput is 'raw_values', then mean absolute error is returned
for each output separately.
If multioutput is 'uniform_average' or an ndarray of weights, then the
weighted average of all output errors is returned.
Examples
--------
>>> from sklearn.metrics import median_absolute_error
>>> y_true = [3, -0.5, 2, 7]
>>> y_pred = [2.5, 0.0, 2, 8]
>>> median_absolute_error(y_true, y_pred)
0.5
>>> y_true = [[0.5, 1], [-1, 1], [7, -6]]
>>> y_pred = [[0, 2], [-1, 2], [8, -5]]
>>> median_absolute_error(y_true, y_pred)
0.75
>>> median_absolute_error(y_true, y_pred, multioutput='raw_values')
array([0.5, 1. ])
>>> median_absolute_error(y_true, y_pred, multioutput=[0.3, 0.7])
0.85
"""
y_type, y_true, y_pred, multioutput = _check_reg_targets(
y_true, y_pred, multioutput)
output_errors = np.median(np.abs(y_pred - y_true), axis=0)
if isinstance(multioutput, str):
if multioutput == 'raw_values':
return output_errors
elif multioutput == 'uniform_average':
# pass None as weights to np.average: uniform mean
multioutput = None
return np.average(output_errors, weights=multioutput)
def explained_variance_score(y_true, y_pred,
sample_weight=None,
multioutput='uniform_average'):
"""Explained variance regression score function
Best possible score is 1.0, lower values are worse.
Read more in the :ref:`User Guide <explained_variance_score>`.
Parameters
----------
y_true : array-like of shape (n_samples,) or (n_samples, n_outputs)
Ground truth (correct) target values.
y_pred : array-like of shape (n_samples,) or (n_samples, n_outputs)
Estimated target values.
sample_weight : array-like of shape (n_samples,), optional
Sample weights.
multioutput : string in ['raw_values', 'uniform_average', \
'variance_weighted'] or array-like of shape (n_outputs)
Defines aggregating of multiple output scores.
Array-like value defines weights used to average scores.
'raw_values' :
Returns a full set of scores in case of multioutput input.
'uniform_average' :
Scores of all outputs are averaged with uniform weight.
'variance_weighted' :
Scores of all outputs are averaged, weighted by the variances
of each individual output.
Returns
-------
score : float or ndarray of floats
The explained variance or ndarray if 'multioutput' is 'raw_values'.
Notes
-----
This is not a symmetric function.
Examples
--------
>>> from sklearn.metrics import explained_variance_score
>>> y_true = [3, -0.5, 2, 7]
>>> y_pred = [2.5, 0.0, 2, 8]
>>> explained_variance_score(y_true, y_pred)
0.957...
>>> y_true = [[0.5, 1], [-1, 1], [7, -6]]
>>> y_pred = [[0, 2], [-1, 2], [8, -5]]
>>> explained_variance_score(y_true, y_pred, multioutput='uniform_average')
0.983...
"""
y_type, y_true, y_pred, multioutput = _check_reg_targets(
y_true, y_pred, multioutput)
check_consistent_length(y_true, y_pred, sample_weight)
y_diff_avg = np.average(y_true - y_pred, weights=sample_weight, axis=0)
numerator = np.average((y_true - y_pred - y_diff_avg) ** 2,
weights=sample_weight, axis=0)
y_true_avg = np.average(y_true, weights=sample_weight, axis=0)
denominator = np.average((y_true - y_true_avg) ** 2,
weights=sample_weight, axis=0)
nonzero_numerator = numerator != 0
nonzero_denominator = denominator != 0
valid_score = nonzero_numerator & nonzero_denominator
output_scores = np.ones(y_true.shape[1])
output_scores[valid_score] = 1 - (numerator[valid_score] /
denominator[valid_score])
output_scores[nonzero_numerator & ~nonzero_denominator] = 0.
if isinstance(multioutput, str):
if multioutput == 'raw_values':
# return scores individually
return output_scores
elif multioutput == 'uniform_average':
# passing to np.average() None as weights results is uniform mean
avg_weights = None
elif multioutput == 'variance_weighted':
avg_weights = denominator
else:
avg_weights = multioutput
return np.average(output_scores, weights=avg_weights)
def r2_score(y_true, y_pred, sample_weight=None,
multioutput="uniform_average"):
"""R^2 (coefficient of determination) regression score function.
Best possible score is 1.0 and it can be negative (because the
model can be arbitrarily worse). A constant model that always
predicts the expected value of y, disregarding the input features,
would get a R^2 score of 0.0.
Read more in the :ref:`User Guide <r2_score>`.
Parameters
----------
y_true : array-like of shape (n_samples,) or (n_samples, n_outputs)
Ground truth (correct) target values.
y_pred : array-like of shape (n_samples,) or (n_samples, n_outputs)
Estimated target values.
sample_weight : array-like of shape (n_samples,), optional
Sample weights.
multioutput : string in ['raw_values', 'uniform_average', \
'variance_weighted'] or None or array-like of shape (n_outputs)
Defines aggregating of multiple output scores.
Array-like value defines weights used to average scores.
Default is "uniform_average".
'raw_values' :
Returns a full set of scores in case of multioutput input.
'uniform_average' :
Scores of all outputs are averaged with uniform weight.
'variance_weighted' :
Scores of all outputs are averaged, weighted by the variances
of each individual output.
.. versionchanged:: 0.19
Default value of multioutput is 'uniform_average'.
Returns
-------
z : float or ndarray of floats
The R^2 score or ndarray of scores if 'multioutput' is
'raw_values'.
Notes
-----
This is not a symmetric function.
Unlike most other scores, R^2 score may be negative (it need not actually
be the square of a quantity R).
This metric is not well-defined for single samples and will return a NaN
value if n_samples is less than two.
References
----------
.. [1] `Wikipedia entry on the Coefficient of determination
<https://en.wikipedia.org/wiki/Coefficient_of_determination>`_
Examples
--------
>>> from sklearn.metrics import r2_score
>>> y_true = [3, -0.5, 2, 7]
>>> y_pred = [2.5, 0.0, 2, 8]
>>> r2_score(y_true, y_pred)
0.948...
>>> y_true = [[0.5, 1], [-1, 1], [7, -6]]
>>> y_pred = [[0, 2], [-1, 2], [8, -5]]
>>> r2_score(y_true, y_pred,
... multioutput='variance_weighted')
0.938...
>>> y_true = [1, 2, 3]
>>> y_pred = [1, 2, 3]
>>> r2_score(y_true, y_pred)
1.0
>>> y_true = [1, 2, 3]
>>> y_pred = [2, 2, 2]
>>> r2_score(y_true, y_pred)
0.0
>>> y_true = [1, 2, 3]
>>> y_pred = [3, 2, 1]
>>> r2_score(y_true, y_pred)
-3.0
"""
y_type, y_true, y_pred, multioutput = _check_reg_targets(
y_true, y_pred, multioutput)
check_consistent_length(y_true, y_pred, sample_weight)
if _num_samples(y_pred) < 2:
msg = "R^2 score is not well-defined with less than two samples."
warnings.warn(msg, UndefinedMetricWarning)
return float('nan')
if sample_weight is not None:
sample_weight = column_or_1d(sample_weight)
weight = sample_weight[:, np.newaxis]
else:
weight = 1.
numerator = (weight * (y_true - y_pred) ** 2).sum(axis=0,
dtype=np.float64)
denominator = (weight * (y_true - np.average(
y_true, axis=0, weights=sample_weight)) ** 2).sum(axis=0,
dtype=np.float64)
nonzero_denominator = denominator != 0
nonzero_numerator = numerator != 0
valid_score = nonzero_denominator & nonzero_numerator
output_scores = np.ones([y_true.shape[1]])
output_scores[valid_score] = 1 - (numerator[valid_score] /
denominator[valid_score])
# arbitrary set to zero to avoid -inf scores, having a constant
# y_true is not interesting for scoring a regression anyway
output_scores[nonzero_numerator & ~nonzero_denominator] = 0.
if isinstance(multioutput, str):
if multioutput == 'raw_values':
# return scores individually
return output_scores
elif multioutput == 'uniform_average':
# passing None as weights results is uniform mean
avg_weights = None
elif multioutput == 'variance_weighted':
avg_weights = denominator
# avoid fail on constant y or one-element arrays
if not np.any(nonzero_denominator):
if not np.any(nonzero_numerator):
return 1.0
else:
return 0.0
else:
avg_weights = multioutput
return np.average(output_scores, weights=avg_weights)
def max_error(y_true, y_pred):
"""
max_error metric calculates the maximum residual error.
Read more in the :ref:`User Guide <max_error>`.
Parameters
----------
y_true : array-like of shape (n_samples,)
Ground truth (correct) target values.
y_pred : array-like of shape (n_samples,)
Estimated target values.
Returns
-------
max_error : float
A positive floating point value (the best value is 0.0).
Examples
--------
>>> from sklearn.metrics import max_error
>>> y_true = [3, 2, 7, 1]
>>> y_pred = [4, 2, 7, 1]
>>> max_error(y_true, y_pred)
1
"""
y_type, y_true, y_pred, _ = _check_reg_targets(y_true, y_pred, None)
if y_type == 'continuous-multioutput':
raise ValueError("Multioutput not supported in max_error")
return np.max(np.abs(y_true - y_pred))
def mean_tweedie_deviance(y_true, y_pred, sample_weight=None, power=0):
"""Mean Tweedie deviance regression loss.
Read more in the :ref:`User Guide <mean_tweedie_deviance>`.
Parameters
----------
y_true : array-like of shape (n_samples,)
Ground truth (correct) target values.
y_pred : array-like of shape (n_samples,)
Estimated target values.
sample_weight : array-like, shape (n_samples,), optional
Sample weights.
power : float, default=0
Tweedie power parameter. Either power <= 0 or power >= 1.
The higher `p` the less weight is given to extreme
deviations between true and predicted targets.
- power < 0: Extreme stable distribution. Requires: y_pred > 0.
- power = 0 : Normal distribution, output corresponds to
mean_squared_error. y_true and y_pred can be any real numbers.
- power = 1 : Poisson distribution. Requires: y_true >= 0 and
y_pred > 0.
- 1 < p < 2 : Compound Poisson distribution. Requires: y_true >= 0
and y_pred > 0.
- power = 2 : Gamma distribution. Requires: y_true > 0 and y_pred > 0.
- power = 3 : Inverse Gaussian distribution. Requires: y_true > 0
and y_pred > 0.
- otherwise : Positive stable distribution. Requires: y_true > 0
and y_pred > 0.
Returns
-------
loss : float
A non-negative floating point value (the best value is 0.0).
Examples
--------
>>> from sklearn.metrics import mean_tweedie_deviance
>>> y_true = [2, 0, 1, 4]
>>> y_pred = [0.5, 0.5, 2., 2.]
>>> mean_tweedie_deviance(y_true, y_pred, power=1)
1.4260...
"""
y_type, y_true, y_pred, _ = _check_reg_targets(
y_true, y_pred, None, dtype=[np.float64, np.float32])
if y_type == 'continuous-multioutput':
raise ValueError("Multioutput not supported in mean_tweedie_deviance")
check_consistent_length(y_true, y_pred, sample_weight)
if sample_weight is not None:
sample_weight = column_or_1d(sample_weight)
sample_weight = sample_weight[:, np.newaxis]
message = ("Mean Tweedie deviance error with power={} can only be used on "
.format(power))
if power < 0:
# 'Extreme stable', y_true any real number, y_pred > 0
if (y_pred <= 0).any():
raise ValueError(message + "strictly positive y_pred.")
dev = 2 * (np.power(np.maximum(y_true, 0), 2 - power)
/ ((1 - power) * (2 - power))
- y_true * np.power(y_pred, 1 - power)/(1 - power)
+ np.power(y_pred, 2 - power)/(2 - power))
elif power == 0:
# Normal distribution, y_true and y_pred any real number
dev = (y_true - y_pred)**2
elif power < 1:
raise ValueError("Tweedie deviance is only defined for power<=0 and "
"power>=1.")
elif power == 1:
# Poisson distribution, y_true >= 0, y_pred > 0
if (y_true < 0).any() or (y_pred <= 0).any():
raise ValueError(message + "non-negative y_true and strictly "
"positive y_pred.")
dev = 2 * (xlogy(y_true, y_true/y_pred) - y_true + y_pred)
elif power == 2:
# Gamma distribution, y_true and y_pred > 0
if (y_true <= 0).any() or (y_pred <= 0).any():
raise ValueError(message + "strictly positive y_true and y_pred.")
dev = 2 * (np.log(y_pred/y_true) + y_true/y_pred - 1)
else:
if power < 2:
# 1 < p < 2 is Compound Poisson, y_true >= 0, y_pred > 0
if (y_true < 0).any() or (y_pred <= 0).any():
raise ValueError(message + "non-negative y_true and strictly "
"positive y_pred.")
else:
if (y_true <= 0).any() or (y_pred <= 0).any():
raise ValueError(message + "strictly positive y_true and "
"y_pred.")
dev = 2 * (np.power(y_true, 2 - power)/((1 - power) * (2 - power))
- y_true * np.power(y_pred, 1 - power)/(1 - power)
+ np.power(y_pred, 2 - power)/(2 - power))
return np.average(dev, weights=sample_weight)
def mean_poisson_deviance(y_true, y_pred, sample_weight=None):
"""Mean Poisson deviance regression loss.
Poisson deviance is equivalent to the Tweedie deviance with
the power parameter `p=1`.
Read more in the :ref:`User Guide <mean_tweedie_deviance>`.
Parameters
----------
y_true : array-like of shape (n_samples,)
Ground truth (correct) target values. Requires y_true >= 0.
y_pred : array-like of shape (n_samples,)
Estimated target values. Requires y_pred > 0.
sample_weight : array-like, shape (n_samples,), optional
Sample weights.
Returns
-------
loss : float
A non-negative floating point value (the best value is 0.0).
Examples
--------
>>> from sklearn.metrics import mean_poisson_deviance
>>> y_true = [2, 0, 1, 4]
>>> y_pred = [0.5, 0.5, 2., 2.]
>>> mean_poisson_deviance(y_true, y_pred)
1.4260...
"""
return mean_tweedie_deviance(
y_true, y_pred, sample_weight=sample_weight, power=1
)
def mean_gamma_deviance(y_true, y_pred, sample_weight=None):
"""Mean Gamma deviance regression loss.
Gamma deviance is equivalent to the Tweedie deviance with
the power parameter `p=2`. It is invariant to scaling of
the target variable, and mesures relative errors.
Read more in the :ref:`User Guide <mean_tweedie_deviance>`.
Parameters
----------
y_true : array-like of shape (n_samples,)
Ground truth (correct) target values. Requires y_true > 0.
y_pred : array-like of shape (n_samples,)
Estimated target values. Requires y_pred > 0.
sample_weight : array-like, shape (n_samples,), optional
Sample weights.
Returns
-------
loss : float
A non-negative floating point value (the best value is 0.0).
Examples
--------
>>> from sklearn.metrics import mean_gamma_deviance
>>> y_true = [2, 0.5, 1, 4]
>>> y_pred = [0.5, 0.5, 2., 2.]
>>> mean_gamma_deviance(y_true, y_pred)
1.0568...
"""
return mean_tweedie_deviance(
y_true, y_pred, sample_weight=sample_weight, power=2
)