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"""Mixture modeling algorithms."""
# Authors: The scikit-learn developers
# SPDX-License-Identifier: BSD-3-Clause
from sklearn.mixture._bayesian_mixture import BayesianGaussianMixture
from sklearn.mixture._gaussian_mixture import GaussianMixture
__all__ = ["BayesianGaussianMixture", "GaussianMixture"]

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"""Base class for mixture models."""
# Authors: The scikit-learn developers
# SPDX-License-Identifier: BSD-3-Clause
import warnings
from abc import ABCMeta, abstractmethod
from contextlib import nullcontext
from numbers import Integral, Real
from time import time
import numpy as np
from sklearn import cluster
from sklearn.base import BaseEstimator, DensityMixin, _fit_context
from sklearn.cluster import kmeans_plusplus
from sklearn.exceptions import ConvergenceWarning
from sklearn.utils import check_random_state
from sklearn.utils._array_api import (
_convert_to_numpy,
_is_numpy_namespace,
_logsumexp,
_max_precision_float_dtype,
get_namespace,
get_namespace_and_device,
)
from sklearn.utils._param_validation import Interval, StrOptions
from sklearn.utils.validation import check_is_fitted, validate_data
def _check_shape(param, param_shape, name):
"""Validate the shape of the input parameter 'param'.
Parameters
----------
param : array
param_shape : tuple
name : str
"""
if param.shape != param_shape:
raise ValueError(
"The parameter '%s' should have the shape of %s, but got %s"
% (name, param_shape, param.shape)
)
class BaseMixture(DensityMixin, BaseEstimator, metaclass=ABCMeta):
"""Base class for mixture models.
This abstract class specifies an interface for all mixture classes and
provides basic common methods for mixture models.
"""
_parameter_constraints: dict = {
"n_components": [Interval(Integral, 1, None, closed="left")],
"tol": [Interval(Real, 0.0, None, closed="left")],
"reg_covar": [Interval(Real, 0.0, None, closed="left")],
"max_iter": [Interval(Integral, 0, None, closed="left")],
"n_init": [Interval(Integral, 1, None, closed="left")],
"init_params": [
StrOptions({"kmeans", "random", "random_from_data", "k-means++"})
],
"random_state": ["random_state"],
"warm_start": ["boolean"],
"verbose": ["verbose"],
"verbose_interval": [Interval(Integral, 1, None, closed="left")],
}
def __init__(
self,
n_components,
tol,
reg_covar,
max_iter,
n_init,
init_params,
random_state,
warm_start,
verbose,
verbose_interval,
):
self.n_components = n_components
self.tol = tol
self.reg_covar = reg_covar
self.max_iter = max_iter
self.n_init = n_init
self.init_params = init_params
self.random_state = random_state
self.warm_start = warm_start
self.verbose = verbose
self.verbose_interval = verbose_interval
@abstractmethod
def _check_parameters(self, X, xp=None):
"""Check initial parameters of the derived class.
Parameters
----------
X : array-like of shape (n_samples, n_features)
"""
pass
def _initialize_parameters(self, X, random_state, xp=None):
"""Initialize the model parameters.
Parameters
----------
X : array-like of shape (n_samples, n_features)
random_state : RandomState
A random number generator instance that controls the random seed
used for the method chosen to initialize the parameters.
"""
xp, _, device = get_namespace_and_device(X, xp=xp)
n_samples, _ = X.shape
if self.init_params == "kmeans":
resp = np.zeros((n_samples, self.n_components), dtype=X.dtype)
label = (
cluster.KMeans(
n_clusters=self.n_components, n_init=1, random_state=random_state
)
.fit(X)
.labels_
)
resp[np.arange(n_samples), label] = 1
elif self.init_params == "random":
resp = xp.asarray(
random_state.uniform(size=(n_samples, self.n_components)),
dtype=X.dtype,
device=device,
)
resp /= xp.sum(resp, axis=1)[:, xp.newaxis]
elif self.init_params == "random_from_data":
resp = xp.zeros(
(n_samples, self.n_components), dtype=X.dtype, device=device
)
indices = random_state.choice(
n_samples, size=self.n_components, replace=False
)
# TODO: when array API supports __setitem__ with fancy indexing we
# can use the previous code:
# resp[indices, xp.arange(self.n_components)] = 1
# Until then we use a for loop on one dimension.
for col, index in enumerate(indices):
resp[index, col] = 1
elif self.init_params == "k-means++":
resp = np.zeros((n_samples, self.n_components), dtype=X.dtype)
_, indices = kmeans_plusplus(
X,
self.n_components,
random_state=random_state,
)
resp[indices, np.arange(self.n_components)] = 1
self._initialize(X, resp)
@abstractmethod
def _initialize(self, X, resp):
"""Initialize the model parameters of the derived class.
Parameters
----------
X : array-like of shape (n_samples, n_features)
resp : array-like of shape (n_samples, n_components)
"""
pass
def fit(self, X, y=None):
"""Estimate model parameters with the EM algorithm.
The method fits the model ``n_init`` times and sets the parameters with
which the model has the largest likelihood or lower bound. Within each
trial, the method iterates between E-step and M-step for ``max_iter``
times until the change of likelihood or lower bound is less than
``tol``, otherwise, a ``ConvergenceWarning`` is raised.
If ``warm_start`` is ``True``, then ``n_init`` is ignored and a single
initialization is performed upon the first call. Upon consecutive
calls, training starts where it left off.
Parameters
----------
X : array-like of shape (n_samples, n_features)
List of n_features-dimensional data points. Each row
corresponds to a single data point.
y : Ignored
Not used, present for API consistency by convention.
Returns
-------
self : object
The fitted mixture.
"""
# parameters are validated in fit_predict
self.fit_predict(X, y)
return self
@_fit_context(prefer_skip_nested_validation=True)
def fit_predict(self, X, y=None):
"""Estimate model parameters using X and predict the labels for X.
The method fits the model ``n_init`` times and sets the parameters with
which the model has the largest likelihood or lower bound. Within each
trial, the method iterates between E-step and M-step for `max_iter`
times until the change of likelihood or lower bound is less than
`tol`, otherwise, a :class:`~sklearn.exceptions.ConvergenceWarning` is
raised. After fitting, it predicts the most probable label for the
input data points.
.. versionadded:: 0.20
Parameters
----------
X : array-like of shape (n_samples, n_features)
List of n_features-dimensional data points. Each row
corresponds to a single data point.
y : Ignored
Not used, present for API consistency by convention.
Returns
-------
labels : array, shape (n_samples,)
Component labels.
"""
xp, _ = get_namespace(X)
X = validate_data(self, X, dtype=[xp.float64, xp.float32], ensure_min_samples=2)
if X.shape[0] < self.n_components:
raise ValueError(
"Expected n_samples >= n_components "
f"but got n_components = {self.n_components}, "
f"n_samples = {X.shape[0]}"
)
self._check_parameters(X, xp=xp)
# if we enable warm_start, we will have a unique initialisation
do_init = not (self.warm_start and hasattr(self, "converged_"))
n_init = self.n_init if do_init else 1
max_lower_bound = -xp.inf
best_lower_bounds = []
self.converged_ = False
random_state = check_random_state(self.random_state)
n_samples, _ = X.shape
for init in range(n_init):
self._print_verbose_msg_init_beg(init)
if do_init:
self._initialize_parameters(X, random_state, xp=xp)
lower_bound = -xp.inf if do_init else self.lower_bound_
current_lower_bounds = []
if self.max_iter == 0:
best_params = self._get_parameters()
best_n_iter = 0
else:
converged = False
for n_iter in range(1, self.max_iter + 1):
prev_lower_bound = lower_bound
log_prob_norm, log_resp = self._e_step(X, xp=xp)
self._m_step(X, log_resp, xp=xp)
lower_bound = self._compute_lower_bound(log_resp, log_prob_norm)
current_lower_bounds.append(lower_bound)
change = lower_bound - prev_lower_bound
self._print_verbose_msg_iter_end(n_iter, change)
if abs(change) < self.tol:
converged = True
break
self._print_verbose_msg_init_end(lower_bound, converged)
if lower_bound > max_lower_bound or max_lower_bound == -xp.inf:
max_lower_bound = lower_bound
best_params = self._get_parameters()
best_n_iter = n_iter
best_lower_bounds = current_lower_bounds
self.converged_ = converged
# Should only warn about convergence if max_iter > 0, otherwise
# the user is assumed to have used 0-iters initialization
# to get the initial means.
if not self.converged_ and self.max_iter > 0:
warnings.warn(
(
"Best performing initialization did not converge. "
"Try different init parameters, or increase max_iter, "
"tol, or check for degenerate data."
),
ConvergenceWarning,
)
self._set_parameters(best_params, xp=xp)
self.n_iter_ = best_n_iter
self.lower_bound_ = max_lower_bound
self.lower_bounds_ = best_lower_bounds
# Always do a final e-step to guarantee that the labels returned by
# fit_predict(X) are always consistent with fit(X).predict(X)
# for any value of max_iter and tol (and any random_state).
_, log_resp = self._e_step(X, xp=xp)
return xp.argmax(log_resp, axis=1)
def _e_step(self, X, xp=None):
"""E step.
Parameters
----------
X : array-like of shape (n_samples, n_features)
Returns
-------
log_prob_norm : float
Mean of the logarithms of the probabilities of each sample in X
log_responsibility : array, shape (n_samples, n_components)
Logarithm of the posterior probabilities (or responsibilities) of
the point of each sample in X.
"""
xp, _ = get_namespace(X, xp=xp)
log_prob_norm, log_resp = self._estimate_log_prob_resp(X, xp=xp)
return xp.mean(log_prob_norm), log_resp
@abstractmethod
def _m_step(self, X, log_resp):
"""M step.
Parameters
----------
X : array-like of shape (n_samples, n_features)
log_resp : array-like of shape (n_samples, n_components)
Logarithm of the posterior probabilities (or responsibilities) of
the point of each sample in X.
"""
pass
@abstractmethod
def _get_parameters(self):
pass
@abstractmethod
def _set_parameters(self, params):
pass
def score_samples(self, X):
"""Compute the log-likelihood of each sample.
Parameters
----------
X : array-like of shape (n_samples, n_features)
List of n_features-dimensional data points. Each row
corresponds to a single data point.
Returns
-------
log_prob : array, shape (n_samples,)
Log-likelihood of each sample in `X` under the current model.
"""
check_is_fitted(self)
X = validate_data(self, X, reset=False)
return _logsumexp(self._estimate_weighted_log_prob(X), axis=1)
def score(self, X, y=None):
"""Compute the per-sample average log-likelihood of the given data X.
Parameters
----------
X : array-like of shape (n_samples, n_dimensions)
List of n_features-dimensional data points. Each row
corresponds to a single data point.
y : Ignored
Not used, present for API consistency by convention.
Returns
-------
log_likelihood : float
Log-likelihood of `X` under the Gaussian mixture model.
"""
xp, _ = get_namespace(X)
return float(xp.mean(self.score_samples(X)))
def predict(self, X):
"""Predict the labels for the data samples in X using trained model.
Parameters
----------
X : array-like of shape (n_samples, n_features)
List of n_features-dimensional data points. Each row
corresponds to a single data point.
Returns
-------
labels : array, shape (n_samples,)
Component labels.
"""
check_is_fitted(self)
xp, _ = get_namespace(X)
X = validate_data(self, X, reset=False)
return xp.argmax(self._estimate_weighted_log_prob(X), axis=1)
def predict_proba(self, X):
"""Evaluate the components' density for each sample.
Parameters
----------
X : array-like of shape (n_samples, n_features)
List of n_features-dimensional data points. Each row
corresponds to a single data point.
Returns
-------
resp : array, shape (n_samples, n_components)
Density of each Gaussian component for each sample in X.
"""
check_is_fitted(self)
X = validate_data(self, X, reset=False)
xp, _ = get_namespace(X)
_, log_resp = self._estimate_log_prob_resp(X, xp=xp)
return xp.exp(log_resp)
def sample(self, n_samples=1):
"""Generate random samples from the fitted Gaussian distribution.
Parameters
----------
n_samples : int, default=1
Number of samples to generate.
Returns
-------
X : array, shape (n_samples, n_features)
Randomly generated sample.
y : array, shape (nsamples,)
Component labels.
"""
check_is_fitted(self)
xp, _, device_ = get_namespace_and_device(self.means_)
if n_samples < 1:
raise ValueError(
"Invalid value for 'n_samples': %d . The sampling requires at "
"least one sample." % (self.n_components)
)
_, n_features = self.means_.shape
rng = check_random_state(self.random_state)
n_samples_comp = rng.multinomial(
n_samples, _convert_to_numpy(self.weights_, xp)
)
if self.covariance_type == "full":
X = np.vstack(
[
rng.multivariate_normal(mean, covariance, int(sample))
for (mean, covariance, sample) in zip(
_convert_to_numpy(self.means_, xp),
_convert_to_numpy(self.covariances_, xp),
n_samples_comp,
)
]
)
elif self.covariance_type == "tied":
X = np.vstack(
[
rng.multivariate_normal(
mean, _convert_to_numpy(self.covariances_, xp), int(sample)
)
for (mean, sample) in zip(
_convert_to_numpy(self.means_, xp), n_samples_comp
)
]
)
else:
X = np.vstack(
[
mean
+ rng.standard_normal(size=(sample, n_features))
* np.sqrt(covariance)
for (mean, covariance, sample) in zip(
_convert_to_numpy(self.means_, xp),
_convert_to_numpy(self.covariances_, xp),
n_samples_comp,
)
]
)
y = xp.concat(
[
xp.full(int(n_samples_comp[i]), i, dtype=xp.int64, device=device_)
for i in range(len(n_samples_comp))
]
)
max_float_dtype = _max_precision_float_dtype(xp=xp, device=device_)
return xp.asarray(X, dtype=max_float_dtype, device=device_), y
def _estimate_weighted_log_prob(self, X, xp=None):
"""Estimate the weighted log-probabilities, log P(X | Z) + log weights.
Parameters
----------
X : array-like of shape (n_samples, n_features)
Returns
-------
weighted_log_prob : array, shape (n_samples, n_component)
"""
return self._estimate_log_prob(X, xp=xp) + self._estimate_log_weights(xp=xp)
@abstractmethod
def _estimate_log_weights(self, xp=None):
"""Estimate log-weights in EM algorithm, E[ log pi ] in VB algorithm.
Returns
-------
log_weight : array, shape (n_components, )
"""
pass
@abstractmethod
def _estimate_log_prob(self, X, xp=None):
"""Estimate the log-probabilities log P(X | Z).
Compute the log-probabilities per each component for each sample.
Parameters
----------
X : array-like of shape (n_samples, n_features)
Returns
-------
log_prob : array, shape (n_samples, n_component)
"""
pass
def _estimate_log_prob_resp(self, X, xp=None):
"""Estimate log probabilities and responsibilities for each sample.
Compute the log probabilities, weighted log probabilities per
component and responsibilities for each sample in X with respect to
the current state of the model.
Parameters
----------
X : array-like of shape (n_samples, n_features)
Returns
-------
log_prob_norm : array, shape (n_samples,)
log p(X)
log_responsibilities : array, shape (n_samples, n_components)
logarithm of the responsibilities
"""
xp, _ = get_namespace(X, xp=xp)
weighted_log_prob = self._estimate_weighted_log_prob(X, xp=xp)
log_prob_norm = _logsumexp(weighted_log_prob, axis=1, xp=xp)
# There is no errstate equivalent for warning/error management in array API
context_manager = (
np.errstate(under="ignore") if _is_numpy_namespace(xp) else nullcontext()
)
with context_manager:
# ignore underflow
log_resp = weighted_log_prob - log_prob_norm[:, xp.newaxis]
return log_prob_norm, log_resp
def _print_verbose_msg_init_beg(self, n_init):
"""Print verbose message on initialization."""
if self.verbose == 1:
print("Initialization %d" % n_init)
elif self.verbose >= 2:
print("Initialization %d" % n_init)
self._init_prev_time = time()
self._iter_prev_time = self._init_prev_time
def _print_verbose_msg_iter_end(self, n_iter, diff_ll):
"""Print verbose message on initialization."""
if n_iter % self.verbose_interval == 0:
if self.verbose == 1:
print(" Iteration %d" % n_iter)
elif self.verbose >= 2:
cur_time = time()
print(
" Iteration %d\t time lapse %.5fs\t ll change %.5f"
% (n_iter, cur_time - self._iter_prev_time, diff_ll)
)
self._iter_prev_time = cur_time
def _print_verbose_msg_init_end(self, lb, init_has_converged):
"""Print verbose message on the end of iteration."""
converged_msg = "converged" if init_has_converged else "did not converge"
if self.verbose == 1:
print(f"Initialization {converged_msg}.")
elif self.verbose >= 2:
t = time() - self._init_prev_time
print(
f"Initialization {converged_msg}. time lapse {t:.5f}s\t lower bound"
f" {lb:.5f}."
)

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"""Bayesian Gaussian Mixture Model."""
# Authors: The scikit-learn developers
# SPDX-License-Identifier: BSD-3-Clause
import math
from numbers import Real
import numpy as np
from scipy.special import betaln, digamma, gammaln
from sklearn.mixture._base import BaseMixture, _check_shape
from sklearn.mixture._gaussian_mixture import (
_check_precision_matrix,
_check_precision_positivity,
_compute_log_det_cholesky,
_compute_precision_cholesky,
_estimate_gaussian_parameters,
_estimate_log_gaussian_prob,
)
from sklearn.utils import check_array
from sklearn.utils._param_validation import Interval, StrOptions
def _log_dirichlet_norm(dirichlet_concentration):
"""Compute the log of the Dirichlet distribution normalization term.
Parameters
----------
dirichlet_concentration : array-like of shape (n_samples,)
The parameters values of the Dirichlet distribution.
Returns
-------
log_dirichlet_norm : float
The log normalization of the Dirichlet distribution.
"""
return gammaln(np.sum(dirichlet_concentration)) - np.sum(
gammaln(dirichlet_concentration)
)
def _log_wishart_norm(degrees_of_freedom, log_det_precisions_chol, n_features):
"""Compute the log of the Wishart distribution normalization term.
Parameters
----------
degrees_of_freedom : array-like of shape (n_components,)
The number of degrees of freedom on the covariance Wishart
distributions.
log_det_precision_chol : array-like of shape (n_components,)
The determinant of the precision matrix for each component.
n_features : int
The number of features.
Return
------
log_wishart_norm : array-like of shape (n_components,)
The log normalization of the Wishart distribution.
"""
# To simplify the computation we have removed the np.log(np.pi) term
return -(
degrees_of_freedom * log_det_precisions_chol
+ degrees_of_freedom * n_features * 0.5 * math.log(2.0)
+ np.sum(
gammaln(0.5 * (degrees_of_freedom - np.arange(n_features)[:, np.newaxis])),
0,
)
)
class BayesianGaussianMixture(BaseMixture):
"""Variational Bayesian estimation of a Gaussian mixture.
This class allows to infer an approximate posterior distribution over the
parameters of a Gaussian mixture distribution. The effective number of
components can be inferred from the data.
This class implements two types of prior for the weights distribution: a
finite mixture model with Dirichlet distribution and an infinite mixture
model with the Dirichlet Process. In practice Dirichlet Process inference
algorithm is approximated and uses a truncated distribution with a fixed
maximum number of components (called the Stick-breaking representation).
The number of components actually used almost always depends on the data.
.. versionadded:: 0.18
Read more in the :ref:`User Guide <bgmm>`.
Parameters
----------
n_components : int, default=1
The number of mixture components. Depending on the data and the value
of the `weight_concentration_prior` the model can decide to not use
all the components by setting some component `weights_` to values very
close to zero. The number of effective components is therefore smaller
than n_components.
covariance_type : {'full', 'tied', 'diag', 'spherical'}, default='full'
String describing the type of covariance parameters to use.
Must be one of:
- 'full' (each component has its own general covariance matrix),
- 'tied' (all components share the same general covariance matrix),
- 'diag' (each component has its own diagonal covariance matrix),
- 'spherical' (each component has its own single variance).
tol : float, default=1e-3
The convergence threshold. EM iterations will stop when the
lower bound average gain on the likelihood (of the training data with
respect to the model) is below this threshold.
reg_covar : float, default=1e-6
Non-negative regularization added to the diagonal of covariance.
Allows to assure that the covariance matrices are all positive.
max_iter : int, default=100
The number of EM iterations to perform.
n_init : int, default=1
The number of initializations to perform. The result with the highest
lower bound value on the likelihood is kept.
init_params : {'kmeans', 'k-means++', 'random', 'random_from_data'}, \
default='kmeans'
The method used to initialize the weights, the means and the
covariances. String must be one of:
- 'kmeans': responsibilities are initialized using kmeans.
- 'k-means++': use the k-means++ method to initialize.
- 'random': responsibilities are initialized randomly.
- 'random_from_data': initial means are randomly selected data points.
.. versionchanged:: v1.1
`init_params` now accepts 'random_from_data' and 'k-means++' as
initialization methods.
weight_concentration_prior_type : {'dirichlet_process', 'dirichlet_distribution'}, \
default='dirichlet_process'
String describing the type of the weight concentration prior.
weight_concentration_prior : float or None, default=None
The dirichlet concentration of each component on the weight
distribution (Dirichlet). This is commonly called gamma in the
literature. The higher concentration puts more mass in
the center and will lead to more components being active, while a lower
concentration parameter will lead to more mass at the edge of the
mixture weights simplex. The value of the parameter must be greater
than 0. If it is None, it's set to ``1. / n_components``.
mean_precision_prior : float or None, default=None
The precision prior on the mean distribution (Gaussian).
Controls the extent of where means can be placed. Larger
values concentrate the cluster means around `mean_prior`.
The value of the parameter must be greater than 0.
If it is None, it is set to 1.
mean_prior : array-like, shape (n_features,), default=None
The prior on the mean distribution (Gaussian).
If it is None, it is set to the mean of X.
degrees_of_freedom_prior : float or None, default=None
The prior of the number of degrees of freedom on the covariance
distributions (Wishart). If it is None, it's set to `n_features`.
covariance_prior : float or array-like, default=None
The prior on the covariance distribution (Wishart).
If it is None, the emiprical covariance prior is initialized using the
covariance of X. The shape depends on `covariance_type`::
(n_features, n_features) if 'full',
(n_features, n_features) if 'tied',
(n_features) if 'diag',
float if 'spherical'
random_state : int, RandomState instance or None, default=None
Controls the random seed given to the method chosen to initialize the
parameters (see `init_params`).
In addition, it controls the generation of random samples from the
fitted distribution (see the method `sample`).
Pass an int for reproducible output across multiple function calls.
See :term:`Glossary <random_state>`.
warm_start : bool, default=False
If 'warm_start' is True, the solution of the last fitting is used as
initialization for the next call of fit(). This can speed up
convergence when fit is called several times on similar problems.
See :term:`the Glossary <warm_start>`.
verbose : int, default=0
Enable verbose output. If 1 then it prints the current
initialization and each iteration step. If greater than 1 then
it prints also the log probability and the time needed
for each step.
verbose_interval : int, default=10
Number of iteration done before the next print.
Attributes
----------
weights_ : array-like of shape (n_components,)
The weights of each mixture components.
means_ : array-like of shape (n_components, n_features)
The mean of each mixture component.
covariances_ : array-like
The covariance of each mixture component.
The shape depends on `covariance_type`::
(n_components,) if 'spherical',
(n_features, n_features) if 'tied',
(n_components, n_features) if 'diag',
(n_components, n_features, n_features) if 'full'
precisions_ : array-like
The precision matrices for each component in the mixture. A precision
matrix is the inverse of a covariance matrix. A covariance matrix is
symmetric positive definite so the mixture of Gaussian can be
equivalently parameterized by the precision matrices. Storing the
precision matrices instead of the covariance matrices makes it more
efficient to compute the log-likelihood of new samples at test time.
The shape depends on ``covariance_type``::
(n_components,) if 'spherical',
(n_features, n_features) if 'tied',
(n_components, n_features) if 'diag',
(n_components, n_features, n_features) if 'full'
precisions_cholesky_ : array-like
The Cholesky decomposition of the precision matrices of each mixture
component. A precision matrix is the inverse of a covariance matrix.
A covariance matrix is symmetric positive definite so the mixture of
Gaussian can be equivalently parameterized by the precision matrices.
Storing the precision matrices instead of the covariance matrices makes
it more efficient to compute the log-likelihood of new samples at test
time. The shape depends on ``covariance_type``::
(n_components,) if 'spherical',
(n_features, n_features) if 'tied',
(n_components, n_features) if 'diag',
(n_components, n_features, n_features) if 'full'
converged_ : bool
True when convergence of the best fit of inference was reached, False otherwise.
n_iter_ : int
Number of step used by the best fit of inference to reach the
convergence.
lower_bound_ : float
Lower bound value on the model evidence (of the training data) of the
best fit of inference.
lower_bounds_ : array-like of shape (`n_iter_`,)
The list of lower bound values on the model evidence from each iteration
of the best fit of inference.
weight_concentration_prior_ : tuple or float
The dirichlet concentration of each component on the weight
distribution (Dirichlet). The type depends on
``weight_concentration_prior_type``::
(float, float) if 'dirichlet_process' (Beta parameters),
float if 'dirichlet_distribution' (Dirichlet parameters).
The higher concentration puts more mass in
the center and will lead to more components being active, while a lower
concentration parameter will lead to more mass at the edge of the
simplex.
weight_concentration_ : array-like of shape (n_components,)
The dirichlet concentration of each component on the weight
distribution (Dirichlet).
mean_precision_prior_ : float
The precision prior on the mean distribution (Gaussian).
Controls the extent of where means can be placed.
Larger values concentrate the cluster means around `mean_prior`.
If mean_precision_prior is set to None, `mean_precision_prior_` is set
to 1.
mean_precision_ : array-like of shape (n_components,)
The precision of each components on the mean distribution (Gaussian).
mean_prior_ : array-like of shape (n_features,)
The prior on the mean distribution (Gaussian).
degrees_of_freedom_prior_ : float
The prior of the number of degrees of freedom on the covariance
distributions (Wishart).
degrees_of_freedom_ : array-like of shape (n_components,)
The number of degrees of freedom of each components in the model.
covariance_prior_ : float or array-like
The prior on the covariance distribution (Wishart).
The shape depends on `covariance_type`::
(n_features, n_features) if 'full',
(n_features, n_features) if 'tied',
(n_features) if 'diag',
float if 'spherical'
n_features_in_ : int
Number of features seen during :term:`fit`.
.. versionadded:: 0.24
feature_names_in_ : ndarray of shape (`n_features_in_`,)
Names of features seen during :term:`fit`. Defined only when `X`
has feature names that are all strings.
.. versionadded:: 1.0
See Also
--------
GaussianMixture : Finite Gaussian mixture fit with EM.
References
----------
.. [1] `Bishop, Christopher M. (2006). "Pattern recognition and machine
learning". Vol. 4 No. 4. New York: Springer.
<https://www.springer.com/kr/book/9780387310732>`_
.. [2] `Hagai Attias. (2000). "A Variational Bayesian Framework for
Graphical Models". In Advances in Neural Information Processing
Systems 12.
<https://proceedings.neurips.cc/paper_files/paper/1999/file/74563ba21a90da13dacf2a73e3ddefa7-Paper.pdf>`_
.. [3] `Blei, David M. and Michael I. Jordan. (2006). "Variational
inference for Dirichlet process mixtures". Bayesian analysis 1.1
<https://www.cs.princeton.edu/courses/archive/fall11/cos597C/reading/BleiJordan2005.pdf>`_
Examples
--------
>>> import numpy as np
>>> from sklearn.mixture import BayesianGaussianMixture
>>> X = np.array([[1, 2], [1, 4], [1, 0], [4, 2], [12, 4], [10, 7]])
>>> bgm = BayesianGaussianMixture(n_components=2, random_state=42).fit(X)
>>> bgm.means_
array([[2.49 , 2.29],
[8.45, 4.52 ]])
>>> bgm.predict([[0, 0], [9, 3]])
array([0, 1])
"""
_parameter_constraints: dict = {
**BaseMixture._parameter_constraints,
"covariance_type": [StrOptions({"spherical", "tied", "diag", "full"})],
"weight_concentration_prior_type": [
StrOptions({"dirichlet_process", "dirichlet_distribution"})
],
"weight_concentration_prior": [
None,
Interval(Real, 0.0, None, closed="neither"),
],
"mean_precision_prior": [None, Interval(Real, 0.0, None, closed="neither")],
"mean_prior": [None, "array-like"],
"degrees_of_freedom_prior": [None, Interval(Real, 0.0, None, closed="neither")],
"covariance_prior": [
None,
"array-like",
Interval(Real, 0.0, None, closed="neither"),
],
}
def __init__(
self,
*,
n_components=1,
covariance_type="full",
tol=1e-3,
reg_covar=1e-6,
max_iter=100,
n_init=1,
init_params="kmeans",
weight_concentration_prior_type="dirichlet_process",
weight_concentration_prior=None,
mean_precision_prior=None,
mean_prior=None,
degrees_of_freedom_prior=None,
covariance_prior=None,
random_state=None,
warm_start=False,
verbose=0,
verbose_interval=10,
):
super().__init__(
n_components=n_components,
tol=tol,
reg_covar=reg_covar,
max_iter=max_iter,
n_init=n_init,
init_params=init_params,
random_state=random_state,
warm_start=warm_start,
verbose=verbose,
verbose_interval=verbose_interval,
)
self.covariance_type = covariance_type
self.weight_concentration_prior_type = weight_concentration_prior_type
self.weight_concentration_prior = weight_concentration_prior
self.mean_precision_prior = mean_precision_prior
self.mean_prior = mean_prior
self.degrees_of_freedom_prior = degrees_of_freedom_prior
self.covariance_prior = covariance_prior
def _check_parameters(self, X, xp=None):
"""Check that the parameters are well defined.
Parameters
----------
X : array-like of shape (n_samples, n_features)
"""
self._check_weights_parameters()
self._check_means_parameters(X)
self._check_precision_parameters(X)
self._checkcovariance_prior_parameter(X)
def _check_weights_parameters(self):
"""Check the parameter of the Dirichlet distribution."""
if self.weight_concentration_prior is None:
self.weight_concentration_prior_ = 1.0 / self.n_components
else:
self.weight_concentration_prior_ = self.weight_concentration_prior
def _check_means_parameters(self, X):
"""Check the parameters of the Gaussian distribution.
Parameters
----------
X : array-like of shape (n_samples, n_features)
"""
_, n_features = X.shape
if self.mean_precision_prior is None:
self.mean_precision_prior_ = 1.0
else:
self.mean_precision_prior_ = self.mean_precision_prior
if self.mean_prior is None:
self.mean_prior_ = X.mean(axis=0)
else:
self.mean_prior_ = check_array(
self.mean_prior, dtype=[np.float64, np.float32], ensure_2d=False
)
_check_shape(self.mean_prior_, (n_features,), "means")
def _check_precision_parameters(self, X):
"""Check the prior parameters of the precision distribution.
Parameters
----------
X : array-like of shape (n_samples, n_features)
"""
_, n_features = X.shape
if self.degrees_of_freedom_prior is None:
self.degrees_of_freedom_prior_ = n_features
elif self.degrees_of_freedom_prior > n_features - 1.0:
self.degrees_of_freedom_prior_ = self.degrees_of_freedom_prior
else:
raise ValueError(
"The parameter 'degrees_of_freedom_prior' "
"should be greater than %d, but got %.3f."
% (n_features - 1, self.degrees_of_freedom_prior)
)
def _checkcovariance_prior_parameter(self, X):
"""Check the `covariance_prior_`.
Parameters
----------
X : array-like of shape (n_samples, n_features)
"""
_, n_features = X.shape
if self.covariance_prior is None:
self.covariance_prior_ = {
"full": np.atleast_2d(np.cov(X.T)),
"tied": np.atleast_2d(np.cov(X.T)),
"diag": np.var(X, axis=0, ddof=1),
"spherical": np.var(X, axis=0, ddof=1).mean(),
}[self.covariance_type]
elif self.covariance_type in ["full", "tied"]:
self.covariance_prior_ = check_array(
self.covariance_prior, dtype=[np.float64, np.float32], ensure_2d=False
)
_check_shape(
self.covariance_prior_,
(n_features, n_features),
"%s covariance_prior" % self.covariance_type,
)
_check_precision_matrix(self.covariance_prior_, self.covariance_type)
elif self.covariance_type == "diag":
self.covariance_prior_ = check_array(
self.covariance_prior, dtype=[np.float64, np.float32], ensure_2d=False
)
_check_shape(
self.covariance_prior_,
(n_features,),
"%s covariance_prior" % self.covariance_type,
)
_check_precision_positivity(self.covariance_prior_, self.covariance_type)
# spherical case
else:
self.covariance_prior_ = self.covariance_prior
def _initialize(self, X, resp):
"""Initialization of the mixture parameters.
Parameters
----------
X : array-like of shape (n_samples, n_features)
resp : array-like of shape (n_samples, n_components)
"""
nk, xk, sk = _estimate_gaussian_parameters(
X, resp, self.reg_covar, self.covariance_type
)
self._estimate_weights(nk)
self._estimate_means(nk, xk)
self._estimate_precisions(nk, xk, sk)
def _estimate_weights(self, nk):
"""Estimate the parameters of the Dirichlet distribution.
Parameters
----------
nk : array-like of shape (n_components,)
"""
if self.weight_concentration_prior_type == "dirichlet_process":
# For dirichlet process weight_concentration will be a tuple
# containing the two parameters of the beta distribution
self.weight_concentration_ = (
1.0 + nk,
(
self.weight_concentration_prior_
+ np.hstack((np.cumsum(nk[::-1])[-2::-1], 0))
),
)
else:
# case Variational Gaussian mixture with dirichlet distribution
self.weight_concentration_ = self.weight_concentration_prior_ + nk
def _estimate_means(self, nk, xk):
"""Estimate the parameters of the Gaussian distribution.
Parameters
----------
nk : array-like of shape (n_components,)
xk : array-like of shape (n_components, n_features)
"""
self.mean_precision_ = self.mean_precision_prior_ + nk
self.means_ = (
self.mean_precision_prior_ * self.mean_prior_ + nk[:, np.newaxis] * xk
) / self.mean_precision_[:, np.newaxis]
def _estimate_precisions(self, nk, xk, sk):
"""Estimate the precisions parameters of the precision distribution.
Parameters
----------
nk : array-like of shape (n_components,)
xk : array-like of shape (n_components, n_features)
sk : array-like
The shape depends of `covariance_type`:
'full' : (n_components, n_features, n_features)
'tied' : (n_features, n_features)
'diag' : (n_components, n_features)
'spherical' : (n_components,)
"""
{
"full": self._estimate_wishart_full,
"tied": self._estimate_wishart_tied,
"diag": self._estimate_wishart_diag,
"spherical": self._estimate_wishart_spherical,
}[self.covariance_type](nk, xk, sk)
self.precisions_cholesky_ = _compute_precision_cholesky(
self.covariances_, self.covariance_type
)
def _estimate_wishart_full(self, nk, xk, sk):
"""Estimate the full Wishart distribution parameters.
Parameters
----------
X : array-like of shape (n_samples, n_features)
nk : array-like of shape (n_components,)
xk : array-like of shape (n_components, n_features)
sk : array-like of shape (n_components, n_features, n_features)
"""
_, n_features = xk.shape
# Warning : in some Bishop book, there is a typo on the formula 10.63
# `degrees_of_freedom_k = degrees_of_freedom_0 + Nk` is
# the correct formula
self.degrees_of_freedom_ = self.degrees_of_freedom_prior_ + nk
self.covariances_ = np.empty((self.n_components, n_features, n_features))
for k in range(self.n_components):
diff = xk[k] - self.mean_prior_
self.covariances_[k] = (
self.covariance_prior_
+ nk[k] * sk[k]
+ nk[k]
* self.mean_precision_prior_
/ self.mean_precision_[k]
* np.outer(diff, diff)
)
# Contrary to the original bishop book, we normalize the covariances
self.covariances_ /= self.degrees_of_freedom_[:, np.newaxis, np.newaxis]
def _estimate_wishart_tied(self, nk, xk, sk):
"""Estimate the tied Wishart distribution parameters.
Parameters
----------
X : array-like of shape (n_samples, n_features)
nk : array-like of shape (n_components,)
xk : array-like of shape (n_components, n_features)
sk : array-like of shape (n_features, n_features)
"""
_, n_features = xk.shape
# Warning : in some Bishop book, there is a typo on the formula 10.63
# `degrees_of_freedom_k = degrees_of_freedom_0 + Nk`
# is the correct formula
self.degrees_of_freedom_ = (
self.degrees_of_freedom_prior_ + nk.sum() / self.n_components
)
diff = xk - self.mean_prior_
self.covariances_ = (
self.covariance_prior_
+ sk * nk.sum() / self.n_components
+ self.mean_precision_prior_
/ self.n_components
* np.dot((nk / self.mean_precision_) * diff.T, diff)
)
# Contrary to the original bishop book, we normalize the covariances
self.covariances_ /= self.degrees_of_freedom_
def _estimate_wishart_diag(self, nk, xk, sk):
"""Estimate the diag Wishart distribution parameters.
Parameters
----------
X : array-like of shape (n_samples, n_features)
nk : array-like of shape (n_components,)
xk : array-like of shape (n_components, n_features)
sk : array-like of shape (n_components, n_features)
"""
_, n_features = xk.shape
# Warning : in some Bishop book, there is a typo on the formula 10.63
# `degrees_of_freedom_k = degrees_of_freedom_0 + Nk`
# is the correct formula
self.degrees_of_freedom_ = self.degrees_of_freedom_prior_ + nk
diff = xk - self.mean_prior_
self.covariances_ = self.covariance_prior_ + nk[:, np.newaxis] * (
sk
+ (self.mean_precision_prior_ / self.mean_precision_)[:, np.newaxis]
* np.square(diff)
)
# Contrary to the original bishop book, we normalize the covariances
self.covariances_ /= self.degrees_of_freedom_[:, np.newaxis]
def _estimate_wishart_spherical(self, nk, xk, sk):
"""Estimate the spherical Wishart distribution parameters.
Parameters
----------
X : array-like of shape (n_samples, n_features)
nk : array-like of shape (n_components,)
xk : array-like of shape (n_components, n_features)
sk : array-like of shape (n_components,)
"""
_, n_features = xk.shape
# Warning : in some Bishop book, there is a typo on the formula 10.63
# `degrees_of_freedom_k = degrees_of_freedom_0 + Nk`
# is the correct formula
self.degrees_of_freedom_ = self.degrees_of_freedom_prior_ + nk
diff = xk - self.mean_prior_
self.covariances_ = self.covariance_prior_ + nk * (
sk
+ self.mean_precision_prior_
/ self.mean_precision_
* np.mean(np.square(diff), 1)
)
# Contrary to the original bishop book, we normalize the covariances
self.covariances_ /= self.degrees_of_freedom_
def _m_step(self, X, log_resp, xp=None):
"""M step.
Parameters
----------
X : array-like of shape (n_samples, n_features)
log_resp : array-like of shape (n_samples, n_components)
Logarithm of the posterior probabilities (or responsibilities) of
the point of each sample in X.
"""
n_samples, _ = X.shape
nk, xk, sk = _estimate_gaussian_parameters(
X, np.exp(log_resp), self.reg_covar, self.covariance_type
)
self._estimate_weights(nk)
self._estimate_means(nk, xk)
self._estimate_precisions(nk, xk, sk)
def _estimate_log_weights(self, xp=None):
if self.weight_concentration_prior_type == "dirichlet_process":
digamma_sum = digamma(
self.weight_concentration_[0] + self.weight_concentration_[1]
)
digamma_a = digamma(self.weight_concentration_[0])
digamma_b = digamma(self.weight_concentration_[1])
return (
digamma_a
- digamma_sum
+ np.hstack((0, np.cumsum(digamma_b - digamma_sum)[:-1]))
)
else:
# case Variational Gaussian mixture with dirichlet distribution
return digamma(self.weight_concentration_) - digamma(
np.sum(self.weight_concentration_)
)
def _estimate_log_prob(self, X, xp=None):
_, n_features = X.shape
# We remove `n_features * np.log(self.degrees_of_freedom_)` because
# the precision matrix is normalized
log_gauss = _estimate_log_gaussian_prob(
X, self.means_, self.precisions_cholesky_, self.covariance_type
) - 0.5 * n_features * np.log(self.degrees_of_freedom_)
log_lambda = n_features * np.log(2.0) + np.sum(
digamma(
0.5
* (self.degrees_of_freedom_ - np.arange(0, n_features)[:, np.newaxis])
),
0,
)
return log_gauss + 0.5 * (log_lambda - n_features / self.mean_precision_)
def _compute_lower_bound(self, log_resp, log_prob_norm):
"""Estimate the lower bound of the model.
The lower bound on the likelihood (of the training data with respect to
the model) is used to detect the convergence and has to increase at
each iteration.
Parameters
----------
X : array-like of shape (n_samples, n_features)
log_resp : array, shape (n_samples, n_components)
Logarithm of the posterior probabilities (or responsibilities) of
the point of each sample in X.
log_prob_norm : float
Logarithm of the probability of each sample in X.
Returns
-------
lower_bound : float
"""
# Contrary to the original formula, we have done some simplification
# and removed all the constant terms.
(n_features,) = self.mean_prior_.shape
# We removed `.5 * n_features * np.log(self.degrees_of_freedom_)`
# because the precision matrix is normalized.
log_det_precisions_chol = _compute_log_det_cholesky(
self.precisions_cholesky_, self.covariance_type, n_features
) - 0.5 * n_features * np.log(self.degrees_of_freedom_)
if self.covariance_type == "tied":
log_wishart = self.n_components * np.float64(
_log_wishart_norm(
self.degrees_of_freedom_, log_det_precisions_chol, n_features
)
)
else:
log_wishart = np.sum(
_log_wishart_norm(
self.degrees_of_freedom_, log_det_precisions_chol, n_features
)
)
if self.weight_concentration_prior_type == "dirichlet_process":
log_norm_weight = -np.sum(
betaln(self.weight_concentration_[0], self.weight_concentration_[1])
)
else:
log_norm_weight = _log_dirichlet_norm(self.weight_concentration_)
return (
-np.sum(np.exp(log_resp) * log_resp)
- log_wishart
- log_norm_weight
- 0.5 * n_features * np.sum(np.log(self.mean_precision_))
)
def _get_parameters(self):
return (
self.weight_concentration_,
self.mean_precision_,
self.means_,
self.degrees_of_freedom_,
self.covariances_,
self.precisions_cholesky_,
)
def _set_parameters(self, params, xp=None):
(
self.weight_concentration_,
self.mean_precision_,
self.means_,
self.degrees_of_freedom_,
self.covariances_,
self.precisions_cholesky_,
) = params
# Weights computation
if self.weight_concentration_prior_type == "dirichlet_process":
weight_dirichlet_sum = (
self.weight_concentration_[0] + self.weight_concentration_[1]
)
tmp = self.weight_concentration_[1] / weight_dirichlet_sum
self.weights_ = (
self.weight_concentration_[0]
/ weight_dirichlet_sum
* np.hstack((1, np.cumprod(tmp[:-1])))
)
self.weights_ /= np.sum(self.weights_)
else:
self.weights_ = self.weight_concentration_ / np.sum(
self.weight_concentration_
)
# Precisions matrices computation
if self.covariance_type == "full":
self.precisions_ = np.array(
[
np.dot(prec_chol, prec_chol.T)
for prec_chol in self.precisions_cholesky_
]
)
elif self.covariance_type == "tied":
self.precisions_ = np.dot(
self.precisions_cholesky_, self.precisions_cholesky_.T
)
else:
self.precisions_ = self.precisions_cholesky_**2

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@@ -0,0 +1,464 @@
# Authors: The scikit-learn developers
# SPDX-License-Identifier: BSD-3-Clause
import copy
import numpy as np
import pytest
from scipy.special import gammaln
from sklearn.exceptions import NotFittedError
from sklearn.metrics.cluster import adjusted_rand_score
from sklearn.mixture import BayesianGaussianMixture
from sklearn.mixture._bayesian_mixture import _log_dirichlet_norm, _log_wishart_norm
from sklearn.mixture.tests.test_gaussian_mixture import RandomData
from sklearn.utils._testing import (
assert_almost_equal,
assert_array_equal,
)
COVARIANCE_TYPE = ["full", "tied", "diag", "spherical"]
PRIOR_TYPE = ["dirichlet_process", "dirichlet_distribution"]
def test_log_dirichlet_norm():
rng = np.random.RandomState(0)
weight_concentration = rng.rand(2)
expected_norm = gammaln(np.sum(weight_concentration)) - np.sum(
gammaln(weight_concentration)
)
predected_norm = _log_dirichlet_norm(weight_concentration)
assert_almost_equal(expected_norm, predected_norm)
def test_log_wishart_norm():
rng = np.random.RandomState(0)
n_components, n_features = 5, 2
degrees_of_freedom = np.abs(rng.rand(n_components)) + 1.0
log_det_precisions_chol = n_features * np.log(range(2, 2 + n_components))
expected_norm = np.empty(5)
for k, (degrees_of_freedom_k, log_det_k) in enumerate(
zip(degrees_of_freedom, log_det_precisions_chol)
):
expected_norm[k] = -(
degrees_of_freedom_k * (log_det_k + 0.5 * n_features * np.log(2.0))
+ np.sum(
gammaln(
0.5
* (degrees_of_freedom_k - np.arange(0, n_features)[:, np.newaxis])
),
0,
)
).item()
predected_norm = _log_wishart_norm(
degrees_of_freedom, log_det_precisions_chol, n_features
)
assert_almost_equal(expected_norm, predected_norm)
def test_bayesian_mixture_weights_prior_initialisation():
rng = np.random.RandomState(0)
n_samples, n_components, n_features = 10, 5, 2
X = rng.rand(n_samples, n_features)
# Check correct init for a given value of weight_concentration_prior
weight_concentration_prior = rng.rand()
bgmm = BayesianGaussianMixture(
weight_concentration_prior=weight_concentration_prior, random_state=rng
).fit(X)
assert_almost_equal(weight_concentration_prior, bgmm.weight_concentration_prior_)
# Check correct init for the default value of weight_concentration_prior
bgmm = BayesianGaussianMixture(n_components=n_components, random_state=rng).fit(X)
assert_almost_equal(1.0 / n_components, bgmm.weight_concentration_prior_)
def test_bayesian_mixture_mean_prior_initialisation():
rng = np.random.RandomState(0)
n_samples, n_components, n_features = 10, 3, 2
X = rng.rand(n_samples, n_features)
# Check correct init for a given value of mean_precision_prior
mean_precision_prior = rng.rand()
bgmm = BayesianGaussianMixture(
mean_precision_prior=mean_precision_prior, random_state=rng
).fit(X)
assert_almost_equal(mean_precision_prior, bgmm.mean_precision_prior_)
# Check correct init for the default value of mean_precision_prior
bgmm = BayesianGaussianMixture(random_state=rng).fit(X)
assert_almost_equal(1.0, bgmm.mean_precision_prior_)
# Check correct init for a given value of mean_prior
mean_prior = rng.rand(n_features)
bgmm = BayesianGaussianMixture(
n_components=n_components, mean_prior=mean_prior, random_state=rng
).fit(X)
assert_almost_equal(mean_prior, bgmm.mean_prior_)
# Check correct init for the default value of bemean_priorta
bgmm = BayesianGaussianMixture(n_components=n_components, random_state=rng).fit(X)
assert_almost_equal(X.mean(axis=0), bgmm.mean_prior_)
def test_bayesian_mixture_precisions_prior_initialisation():
rng = np.random.RandomState(0)
n_samples, n_features = 10, 2
X = rng.rand(n_samples, n_features)
# Check raise message for a bad value of degrees_of_freedom_prior
bad_degrees_of_freedom_prior_ = n_features - 1.0
bgmm = BayesianGaussianMixture(
degrees_of_freedom_prior=bad_degrees_of_freedom_prior_, random_state=rng
)
msg = (
"The parameter 'degrees_of_freedom_prior' should be greater than"
f" {n_features - 1}, but got {bad_degrees_of_freedom_prior_:.3f}."
)
with pytest.raises(ValueError, match=msg):
bgmm.fit(X)
# Check correct init for a given value of degrees_of_freedom_prior
degrees_of_freedom_prior = rng.rand() + n_features - 1.0
bgmm = BayesianGaussianMixture(
degrees_of_freedom_prior=degrees_of_freedom_prior, random_state=rng
).fit(X)
assert_almost_equal(degrees_of_freedom_prior, bgmm.degrees_of_freedom_prior_)
# Check correct init for the default value of degrees_of_freedom_prior
degrees_of_freedom_prior_default = n_features
bgmm = BayesianGaussianMixture(
degrees_of_freedom_prior=degrees_of_freedom_prior_default, random_state=rng
).fit(X)
assert_almost_equal(
degrees_of_freedom_prior_default, bgmm.degrees_of_freedom_prior_
)
# Check correct init for a given value of covariance_prior
covariance_prior = {
"full": np.cov(X.T, bias=1) + 10,
"tied": np.cov(X.T, bias=1) + 5,
"diag": np.diag(np.atleast_2d(np.cov(X.T, bias=1))) + 3,
"spherical": rng.rand(),
}
bgmm = BayesianGaussianMixture(random_state=rng)
for cov_type in ["full", "tied", "diag", "spherical"]:
bgmm.covariance_type = cov_type
bgmm.covariance_prior = covariance_prior[cov_type]
bgmm.fit(X)
assert_almost_equal(covariance_prior[cov_type], bgmm.covariance_prior_)
# Check correct init for the default value of covariance_prior
covariance_prior_default = {
"full": np.atleast_2d(np.cov(X.T)),
"tied": np.atleast_2d(np.cov(X.T)),
"diag": np.var(X, axis=0, ddof=1),
"spherical": np.var(X, axis=0, ddof=1).mean(),
}
bgmm = BayesianGaussianMixture(random_state=0)
for cov_type in ["full", "tied", "diag", "spherical"]:
bgmm.covariance_type = cov_type
bgmm.fit(X)
assert_almost_equal(covariance_prior_default[cov_type], bgmm.covariance_prior_)
def test_bayesian_mixture_check_is_fitted():
rng = np.random.RandomState(0)
n_samples, n_features = 10, 2
# Check raise message
bgmm = BayesianGaussianMixture(random_state=rng)
X = rng.rand(n_samples, n_features)
msg = "This BayesianGaussianMixture instance is not fitted yet."
with pytest.raises(ValueError, match=msg):
bgmm.score(X)
def test_bayesian_mixture_weights():
rng = np.random.RandomState(0)
n_samples, n_features = 10, 2
X = rng.rand(n_samples, n_features)
# Case Dirichlet distribution for the weight concentration prior type
bgmm = BayesianGaussianMixture(
weight_concentration_prior_type="dirichlet_distribution",
n_components=3,
random_state=rng,
).fit(X)
expected_weights = bgmm.weight_concentration_ / np.sum(bgmm.weight_concentration_)
assert_almost_equal(expected_weights, bgmm.weights_)
assert_almost_equal(np.sum(bgmm.weights_), 1.0)
# Case Dirichlet process for the weight concentration prior type
dpgmm = BayesianGaussianMixture(
weight_concentration_prior_type="dirichlet_process",
n_components=3,
random_state=rng,
).fit(X)
weight_dirichlet_sum = (
dpgmm.weight_concentration_[0] + dpgmm.weight_concentration_[1]
)
tmp = dpgmm.weight_concentration_[1] / weight_dirichlet_sum
expected_weights = (
dpgmm.weight_concentration_[0]
/ weight_dirichlet_sum
* np.hstack((1, np.cumprod(tmp[:-1])))
)
expected_weights /= np.sum(expected_weights)
assert_almost_equal(expected_weights, dpgmm.weights_)
assert_almost_equal(np.sum(dpgmm.weights_), 1.0)
@pytest.mark.filterwarnings("ignore::sklearn.exceptions.ConvergenceWarning")
def test_monotonic_likelihood():
# We check that each step of the each step of variational inference without
# regularization improve monotonically the training set of the bound
rng = np.random.RandomState(0)
rand_data = RandomData(rng, scale=20)
n_components = rand_data.n_components
for prior_type in PRIOR_TYPE:
for covar_type in COVARIANCE_TYPE:
X = rand_data.X[covar_type]
bgmm = BayesianGaussianMixture(
weight_concentration_prior_type=prior_type,
n_components=2 * n_components,
covariance_type=covar_type,
warm_start=True,
max_iter=1,
random_state=rng,
tol=1e-3,
)
current_lower_bound = -np.inf
# Do one training iteration at a time so we can make sure that the
# training log likelihood increases after each iteration.
for _ in range(600):
prev_lower_bound = current_lower_bound
current_lower_bound = bgmm.fit(X).lower_bound_
assert current_lower_bound >= prev_lower_bound
if bgmm.converged_:
break
assert bgmm.converged_
def test_compare_covar_type():
# We can compare the 'full' precision with the other cov_type if we apply
# 1 iter of the M-step (done during _initialize_parameters).
rng = np.random.RandomState(0)
rand_data = RandomData(rng, scale=7)
X = rand_data.X["full"]
n_components = rand_data.n_components
for prior_type in PRIOR_TYPE:
# Computation of the full_covariance
bgmm = BayesianGaussianMixture(
weight_concentration_prior_type=prior_type,
n_components=2 * n_components,
covariance_type="full",
max_iter=1,
random_state=0,
tol=1e-7,
)
bgmm._check_parameters(X)
bgmm._initialize_parameters(X, np.random.RandomState(0))
full_covariances = (
bgmm.covariances_ * bgmm.degrees_of_freedom_[:, np.newaxis, np.newaxis]
)
# Check tied_covariance = mean(full_covariances, 0)
bgmm = BayesianGaussianMixture(
weight_concentration_prior_type=prior_type,
n_components=2 * n_components,
covariance_type="tied",
max_iter=1,
random_state=0,
tol=1e-7,
)
bgmm._check_parameters(X)
bgmm._initialize_parameters(X, np.random.RandomState(0))
tied_covariance = bgmm.covariances_ * bgmm.degrees_of_freedom_
assert_almost_equal(tied_covariance, np.mean(full_covariances, 0))
# Check diag_covariance = diag(full_covariances)
bgmm = BayesianGaussianMixture(
weight_concentration_prior_type=prior_type,
n_components=2 * n_components,
covariance_type="diag",
max_iter=1,
random_state=0,
tol=1e-7,
)
bgmm._check_parameters(X)
bgmm._initialize_parameters(X, np.random.RandomState(0))
diag_covariances = bgmm.covariances_ * bgmm.degrees_of_freedom_[:, np.newaxis]
assert_almost_equal(
diag_covariances, np.array([np.diag(cov) for cov in full_covariances])
)
# Check spherical_covariance = np.mean(diag_covariances, 0)
bgmm = BayesianGaussianMixture(
weight_concentration_prior_type=prior_type,
n_components=2 * n_components,
covariance_type="spherical",
max_iter=1,
random_state=0,
tol=1e-7,
)
bgmm._check_parameters(X)
bgmm._initialize_parameters(X, np.random.RandomState(0))
spherical_covariances = bgmm.covariances_ * bgmm.degrees_of_freedom_
assert_almost_equal(spherical_covariances, np.mean(diag_covariances, 1))
@pytest.mark.filterwarnings("ignore::sklearn.exceptions.ConvergenceWarning")
def test_check_covariance_precision():
# We check that the dot product of the covariance and the precision
# matrices is identity.
rng = np.random.RandomState(0)
rand_data = RandomData(rng, scale=7)
n_components, n_features = 2 * rand_data.n_components, 2
# Computation of the full_covariance
bgmm = BayesianGaussianMixture(
n_components=n_components, max_iter=100, random_state=rng, tol=1e-3, reg_covar=0
)
for covar_type in COVARIANCE_TYPE:
bgmm.covariance_type = covar_type
bgmm.fit(rand_data.X[covar_type])
if covar_type == "full":
for covar, precision in zip(bgmm.covariances_, bgmm.precisions_):
assert_almost_equal(np.dot(covar, precision), np.eye(n_features))
elif covar_type == "tied":
assert_almost_equal(
np.dot(bgmm.covariances_, bgmm.precisions_), np.eye(n_features)
)
elif covar_type == "diag":
assert_almost_equal(
bgmm.covariances_ * bgmm.precisions_,
np.ones((n_components, n_features)),
)
else:
assert_almost_equal(
bgmm.covariances_ * bgmm.precisions_, np.ones(n_components)
)
def test_invariant_translation():
# We check here that adding a constant in the data change correctly the
# parameters of the mixture
rng = np.random.RandomState(0)
rand_data = RandomData(rng, scale=100)
n_components = 2 * rand_data.n_components
for prior_type in PRIOR_TYPE:
for covar_type in COVARIANCE_TYPE:
X = rand_data.X[covar_type]
bgmm1 = BayesianGaussianMixture(
weight_concentration_prior_type=prior_type,
n_components=n_components,
max_iter=100,
random_state=0,
tol=1e-3,
reg_covar=0,
).fit(X)
bgmm2 = BayesianGaussianMixture(
weight_concentration_prior_type=prior_type,
n_components=n_components,
max_iter=100,
random_state=0,
tol=1e-3,
reg_covar=0,
).fit(X + 100)
assert_almost_equal(bgmm1.means_, bgmm2.means_ - 100)
assert_almost_equal(bgmm1.weights_, bgmm2.weights_)
assert_almost_equal(bgmm1.covariances_, bgmm2.covariances_)
@pytest.mark.filterwarnings("ignore:.*did not converge.*")
@pytest.mark.parametrize(
"seed, max_iter, tol",
[
(0, 2, 1e-7), # strict non-convergence
(1, 2, 1e-1), # loose non-convergence
(3, 300, 1e-7), # strict convergence
(4, 300, 1e-1), # loose convergence
],
)
def test_bayesian_mixture_fit_predict(seed, max_iter, tol):
rng = np.random.RandomState(seed)
rand_data = RandomData(rng, n_samples=50, scale=7)
n_components = 2 * rand_data.n_components
for covar_type in COVARIANCE_TYPE:
bgmm1 = BayesianGaussianMixture(
n_components=n_components,
max_iter=max_iter,
random_state=rng,
tol=tol,
reg_covar=0,
)
bgmm1.covariance_type = covar_type
bgmm2 = copy.deepcopy(bgmm1)
X = rand_data.X[covar_type]
Y_pred1 = bgmm1.fit(X).predict(X)
Y_pred2 = bgmm2.fit_predict(X)
assert_array_equal(Y_pred1, Y_pred2)
def test_bayesian_mixture_fit_predict_n_init():
# Check that fit_predict is equivalent to fit.predict, when n_init > 1
X = np.random.RandomState(0).randn(50, 5)
gm = BayesianGaussianMixture(n_components=5, n_init=10, random_state=0)
y_pred1 = gm.fit_predict(X)
y_pred2 = gm.predict(X)
assert_array_equal(y_pred1, y_pred2)
def test_bayesian_mixture_predict_predict_proba():
# this is the same test as test_gaussian_mixture_predict_predict_proba()
rng = np.random.RandomState(0)
rand_data = RandomData(rng)
for prior_type in PRIOR_TYPE:
for covar_type in COVARIANCE_TYPE:
X = rand_data.X[covar_type]
Y = rand_data.Y
bgmm = BayesianGaussianMixture(
n_components=rand_data.n_components,
random_state=rng,
weight_concentration_prior_type=prior_type,
covariance_type=covar_type,
)
# Check a warning message arrive if we don't do fit
msg = (
"This BayesianGaussianMixture instance is not fitted yet. "
"Call 'fit' with appropriate arguments before using this "
"estimator."
)
with pytest.raises(NotFittedError, match=msg):
bgmm.predict(X)
bgmm.fit(X)
Y_pred = bgmm.predict(X)
Y_pred_proba = bgmm.predict_proba(X).argmax(axis=1)
assert_array_equal(Y_pred, Y_pred_proba)
assert adjusted_rand_score(Y, Y_pred) >= 0.95

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# Authors: The scikit-learn developers
# SPDX-License-Identifier: BSD-3-Clause
import numpy as np
import pytest
from sklearn.base import clone
from sklearn.mixture import BayesianGaussianMixture, GaussianMixture
@pytest.mark.parametrize("estimator", [GaussianMixture(), BayesianGaussianMixture()])
def test_gaussian_mixture_n_iter(estimator):
# check that n_iter is the number of iteration performed.
estimator = clone(estimator) # Avoid side effects from shared instances
rng = np.random.RandomState(0)
X = rng.rand(10, 5)
max_iter = 1
estimator.set_params(max_iter=max_iter)
estimator.fit(X)
assert estimator.n_iter_ == max_iter
@pytest.mark.parametrize("estimator", [GaussianMixture(), BayesianGaussianMixture()])
def test_mixture_n_components_greater_than_n_samples_error(estimator):
"""Check error when n_components <= n_samples"""
estimator = clone(estimator) # Avoid side effects from shared instances
rng = np.random.RandomState(0)
X = rng.rand(10, 5)
estimator.set_params(n_components=12)
msg = "Expected n_samples >= n_components"
with pytest.raises(ValueError, match=msg):
estimator.fit(X)