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/ svm / _classes.py
import warnings
import numpy as np
from ._base import _fit_liblinear, BaseSVC, BaseLibSVM
from ..base import BaseEstimator, RegressorMixin, OutlierMixin
from ..linear_model._base import LinearClassifierMixin, SparseCoefMixin, \
LinearModel
from ..utils import check_X_y
from ..utils.validation import _num_samples
from ..utils.multiclass import check_classification_targets
class LinearSVC(BaseEstimator, LinearClassifierMixin,
SparseCoefMixin):
"""Linear Support Vector Classification.
Similar to SVC with parameter kernel='linear', but implemented in terms of
liblinear rather than libsvm, so it has more flexibility in the choice of
penalties and loss functions and should scale better to large numbers of
samples.
This class supports both dense and sparse input and the multiclass support
is handled according to a one-vs-the-rest scheme.
Read more in the :ref:`User Guide <svm_classification>`.
Parameters
----------
penalty : str, 'l1' or 'l2' (default='l2')
Specifies the norm used in the penalization. The 'l2'
penalty is the standard used in SVC. The 'l1' leads to ``coef_``
vectors that are sparse.
loss : str, 'hinge' or 'squared_hinge' (default='squared_hinge')
Specifies the loss function. 'hinge' is the standard SVM loss
(used e.g. by the SVC class) while 'squared_hinge' is the
square of the hinge loss.
dual : bool, (default=True)
Select the algorithm to either solve the dual or primal
optimization problem. Prefer dual=False when n_samples > n_features.
tol : float, optional (default=1e-4)
Tolerance for stopping criteria.
C : float, optional (default=1.0)
Regularization parameter. The strength of the regularization is
inversely proportional to C. Must be strictly positive.
multi_class : str, 'ovr' or 'crammer_singer' (default='ovr')
Determines the multi-class strategy if `y` contains more than
two classes.
``"ovr"`` trains n_classes one-vs-rest classifiers, while
``"crammer_singer"`` optimizes a joint objective over all classes.
While `crammer_singer` is interesting from a theoretical perspective
as it is consistent, it is seldom used in practice as it rarely leads
to better accuracy and is more expensive to compute.
If ``"crammer_singer"`` is chosen, the options loss, penalty and dual
will be ignored.
fit_intercept : bool, optional (default=True)
Whether to calculate the intercept for this model. If set
to false, no intercept will be used in calculations
(i.e. data is expected to be already centered).
intercept_scaling : float, optional (default=1)
When self.fit_intercept is True, instance vector x becomes
``[x, self.intercept_scaling]``,
i.e. a "synthetic" feature with constant value equals to
intercept_scaling is appended to the instance vector.
The intercept becomes intercept_scaling * synthetic feature weight
Note! the synthetic feature weight is subject to l1/l2 regularization
as all other features.
To lessen the effect of regularization on synthetic feature weight
(and therefore on the intercept) intercept_scaling has to be increased.
class_weight : {dict, 'balanced'}, optional
Set the parameter C of class i to ``class_weight[i]*C`` for
SVC. If not given, all classes are supposed to have
weight one.
The "balanced" mode uses the values of y to automatically adjust
weights inversely proportional to class frequencies in the input data
as ``n_samples / (n_classes * np.bincount(y))``.
verbose : int, (default=0)
Enable verbose output. Note that this setting takes advantage of a
per-process runtime setting in liblinear that, if enabled, may not work
properly in a multithreaded context.
random_state : int, RandomState instance or None, optional (default=None)
The seed of the pseudo random number generator to use when shuffling
the data for the dual coordinate descent (if ``dual=True``). When
``dual=False`` the underlying implementation of :class:`LinearSVC`
is not random and ``random_state`` has no effect on the results. If
int, random_state is the seed used by the random number generator; If
RandomState instance, random_state is the random number generator; If
None, the random number generator is the RandomState instance used by
`np.random`.
max_iter : int, (default=1000)
The maximum number of iterations to be run.
Attributes
----------
coef_ : array, shape = [1, n_features] if n_classes == 2 \
else [n_classes, n_features]
Weights assigned to the features (coefficients in the primal
problem). This is only available in the case of a linear kernel.
``coef_`` is a readonly property derived from ``raw_coef_`` that
follows the internal memory layout of liblinear.
intercept_ : array, shape = [1] if n_classes == 2 else [n_classes]
Constants in decision function.
classes_ : array of shape (n_classes,)
The unique classes labels.
n_iter_ : int
Maximum number of iterations run across all classes.
See Also
--------
SVC
Implementation of Support Vector Machine classifier using libsvm:
the kernel can be non-linear but its SMO algorithm does not
scale to large number of samples as LinearSVC does.
Furthermore SVC multi-class mode is implemented using one
vs one scheme while LinearSVC uses one vs the rest. It is
possible to implement one vs the rest with SVC by using the
:class:`sklearn.multiclass.OneVsRestClassifier` wrapper.
Finally SVC can fit dense data without memory copy if the input
is C-contiguous. Sparse data will still incur memory copy though.
sklearn.linear_model.SGDClassifier
SGDClassifier can optimize the same cost function as LinearSVC
by adjusting the penalty and loss parameters. In addition it requires
less memory, allows incremental (online) learning, and implements
various loss functions and regularization regimes.
Notes
-----
The underlying C implementation uses a random number generator to
select features when fitting the model. It is thus not uncommon
to have slightly different results for the same input data. If
that happens, try with a smaller ``tol`` parameter.
The underlying implementation, liblinear, uses a sparse internal
representation for the data that will incur a memory copy.
Predict output may not match that of standalone liblinear in certain
cases. See :ref:`differences from liblinear <liblinear_differences>`
in the narrative documentation.
References
----------
`LIBLINEAR: A Library for Large Linear Classification
<https://www.csie.ntu.edu.tw/~cjlin/liblinear/>`__
Examples
--------
>>> from sklearn.svm import LinearSVC
>>> from sklearn.datasets import make_classification
>>> X, y = make_classification(n_features=4, random_state=0)
>>> clf = LinearSVC(random_state=0, tol=1e-5)
>>> clf.fit(X, y)
LinearSVC(random_state=0, tol=1e-05)
>>> print(clf.coef_)
[[0.085... 0.394... 0.498... 0.375...]]
>>> print(clf.intercept_)
[0.284...]
>>> print(clf.predict([[0, 0, 0, 0]]))
[1]
"""
def __init__(self, penalty='l2', loss='squared_hinge', dual=True, tol=1e-4,
C=1.0, multi_class='ovr', fit_intercept=True,
intercept_scaling=1, class_weight=None, verbose=0,
random_state=None, max_iter=1000):
self.dual = dual
self.tol = tol
self.C = C
self.multi_class = multi_class
self.fit_intercept = fit_intercept
self.intercept_scaling = intercept_scaling
self.class_weight = class_weight
self.verbose = verbose
self.random_state = random_state
self.max_iter = max_iter
self.penalty = penalty
self.loss = loss
def fit(self, X, y, sample_weight=None):
"""Fit the model according to the given training data.
Parameters
----------
X : {array-like, sparse matrix} of shape (n_samples, n_features)
Training vector, where n_samples in the number of samples and
n_features is the number of features.
y : array-like of shape (n_samples,)
Target vector relative to X.
sample_weight : array-like of shape (n_samples,), default=None
Array of weights that are assigned to individual
samples. If not provided,
then each sample is given unit weight.
Returns
-------
self : object
An instance of the estimator.
"""
# FIXME Remove l1/l2 support in 0.23 ----------------------------------
msg = ("loss='%s' has been deprecated in favor of "
"loss='%s' as of 0.16. Backward compatibility"
" for the loss='%s' will be removed in %s")
if self.loss in ('l1', 'l2'):
old_loss = self.loss
self.loss = {'l1': 'hinge', 'l2': 'squared_hinge'}.get(self.loss)
warnings.warn(msg % (old_loss, self.loss, old_loss, '0.23'),
FutureWarning)
# ---------------------------------------------------------------------
if self.C < 0:
raise ValueError("Penalty term must be positive; got (C=%r)"
% self.C)
X, y = check_X_y(X, y, accept_sparse='csr',
dtype=np.float64, order="C",
accept_large_sparse=False)
check_classification_targets(y)
self.classes_ = np.unique(y)
self.coef_, self.intercept_, self.n_iter_ = _fit_liblinear(
X, y, self.C, self.fit_intercept, self.intercept_scaling,
self.class_weight, self.penalty, self.dual, self.verbose,
self.max_iter, self.tol, self.random_state, self.multi_class,
self.loss, sample_weight=sample_weight)
if self.multi_class == "crammer_singer" and len(self.classes_) == 2:
self.coef_ = (self.coef_[1] - self.coef_[0]).reshape(1, -1)
if self.fit_intercept:
intercept = self.intercept_[1] - self.intercept_[0]
self.intercept_ = np.array([intercept])
return self
class LinearSVR(RegressorMixin, LinearModel):
"""Linear Support Vector Regression.
Similar to SVR with parameter kernel='linear', but implemented in terms of
liblinear rather than libsvm, so it has more flexibility in the choice of
penalties and loss functions and should scale better to large numbers of
samples.
This class supports both dense and sparse input.
Read more in the :ref:`User Guide <svm_regression>`.
.. versionadded:: 0.16
Parameters
----------
epsilon : float, optional (default=0.0)
Epsilon parameter in the epsilon-insensitive loss function. Note
that the value of this parameter depends on the scale of the target
variable y. If unsure, set ``epsilon=0``.
tol : float, optional (default=1e-4)
Tolerance for stopping criteria.
C : float, optional (default=1.0)
Regularization parameter. The strength of the regularization is
inversely proportional to C. Must be strictly positive.
loss : string, optional (default='epsilon_insensitive')
Specifies the loss function. The epsilon-insensitive loss
(standard SVR) is the L1 loss, while the squared epsilon-insensitive
loss ('squared_epsilon_insensitive') is the L2 loss.
fit_intercept : boolean, optional (default=True)
Whether to calculate the intercept for this model. If set
to false, no intercept will be used in calculations
(i.e. data is expected to be already centered).
intercept_scaling : float, optional (default=1)
When self.fit_intercept is True, instance vector x becomes
[x, self.intercept_scaling],
i.e. a "synthetic" feature with constant value equals to
intercept_scaling is appended to the instance vector.
The intercept becomes intercept_scaling * synthetic feature weight
Note! the synthetic feature weight is subject to l1/l2 regularization
as all other features.
To lessen the effect of regularization on synthetic feature weight
(and therefore on the intercept) intercept_scaling has to be increased.
dual : bool, (default=True)
Select the algorithm to either solve the dual or primal
optimization problem. Prefer dual=False when n_samples > n_features.
verbose : int, (default=0)
Enable verbose output. Note that this setting takes advantage of a
per-process runtime setting in liblinear that, if enabled, may not work
properly in a multithreaded context.
random_state : int, RandomState instance or None, optional (default=None)
The seed of the pseudo random number generator to use when shuffling
the data. If int, random_state is the seed used by the random number
generator; If RandomState instance, random_state is the random number
generator; If None, the random number generator is the RandomState
instance used by `np.random`.
max_iter : int, (default=1000)
The maximum number of iterations to be run.
Attributes
----------
coef_ : array, shape = [n_features] if n_classes == 2 else [n_classes, n_features]
Weights assigned to the features (coefficients in the primal
problem). This is only available in the case of a linear kernel.
`coef_` is a readonly property derived from `raw_coef_` that
follows the internal memory layout of liblinear.
intercept_ : array, shape = [1] if n_classes == 2 else [n_classes]
Constants in decision function.
n_iter_ : int
Maximum number of iterations run across all classes.
Examples
--------
>>> from sklearn.svm import LinearSVR
>>> from sklearn.datasets import make_regression
>>> X, y = make_regression(n_features=4, random_state=0)
>>> regr = LinearSVR(random_state=0, tol=1e-5)
>>> regr.fit(X, y)
LinearSVR(random_state=0, tol=1e-05)
>>> print(regr.coef_)
[16.35... 26.91... 42.30... 60.47...]
>>> print(regr.intercept_)
[-4.29...]
>>> print(regr.predict([[0, 0, 0, 0]]))
[-4.29...]
See also
--------
LinearSVC
Implementation of Support Vector Machine classifier using the
same library as this class (liblinear).
SVR
Implementation of Support Vector Machine regression using libsvm:
the kernel can be non-linear but its SMO algorithm does not
scale to large number of samples as LinearSVC does.
sklearn.linear_model.SGDRegressor
SGDRegressor can optimize the same cost function as LinearSVR
by adjusting the penalty and loss parameters. In addition it requires
less memory, allows incremental (online) learning, and implements
various loss functions and regularization regimes.
"""
def __init__(self, epsilon=0.0, tol=1e-4, C=1.0,
loss='epsilon_insensitive', fit_intercept=True,
intercept_scaling=1., dual=True, verbose=0,
random_state=None, max_iter=1000):
self.tol = tol
self.C = C
self.epsilon = epsilon
self.fit_intercept = fit_intercept
self.intercept_scaling = intercept_scaling
self.verbose = verbose
self.random_state = random_state
self.max_iter = max_iter
self.dual = dual
self.loss = loss
def fit(self, X, y, sample_weight=None):
"""Fit the model according to the given training data.
Parameters
----------
X : {array-like, sparse matrix} of shape (n_samples, n_features)
Training vector, where n_samples in the number of samples and
n_features is the number of features.
y : array-like of shape (n_samples,)
Target vector relative to X
sample_weight : array-like of shape (n_samples,), default=None
Array of weights that are assigned to individual
samples. If not provided,
then each sample is given unit weight.
Returns
-------
self : object
"""
# FIXME Remove l1/l2 support in 0.23 ----------------------------------
msg = ("loss='%s' has been deprecated in favor of "
"loss='%s' as of 0.16. Backward compatibility"
" for the loss='%s' will be removed in %s")
if self.loss in ('l1', 'l2'):
old_loss = self.loss
self.loss = {'l1': 'epsilon_insensitive',
'l2': 'squared_epsilon_insensitive'
}.get(self.loss)
warnings.warn(msg % (old_loss, self.loss, old_loss, '0.23'),
FutureWarning)
# ---------------------------------------------------------------------
if self.C < 0:
raise ValueError("Penalty term must be positive; got (C=%r)"
% self.C)
X, y = check_X_y(X, y, accept_sparse='csr',
dtype=np.float64, order="C",
accept_large_sparse=False)
penalty = 'l2' # SVR only accepts l2 penalty
self.coef_, self.intercept_, self.n_iter_ = _fit_liblinear(
X, y, self.C, self.fit_intercept, self.intercept_scaling,
None, penalty, self.dual, self.verbose,
self.max_iter, self.tol, self.random_state, loss=self.loss,
epsilon=self.epsilon, sample_weight=sample_weight)
self.coef_ = self.coef_.ravel()
return self
class SVC(BaseSVC):
"""C-Support Vector Classification.
The implementation is based on libsvm. The fit time scales at least
quadratically with the number of samples and may be impractical
beyond tens of thousands of samples. For large datasets
consider using :class:`sklearn.svm.LinearSVC` or
:class:`sklearn.linear_model.SGDClassifier` instead, possibly after a
:class:`sklearn.kernel_approximation.Nystroem` transformer.
The multiclass support is handled according to a one-vs-one scheme.
For details on the precise mathematical formulation of the provided
kernel functions and how `gamma`, `coef0` and `degree` affect each
other, see the corresponding section in the narrative documentation:
:ref:`svm_kernels`.
Read more in the :ref:`User Guide <svm_classification>`.
Parameters
----------
C : float, optional (default=1.0)
Regularization parameter. The strength of the regularization is
inversely proportional to C. Must be strictly positive. The penalty
is a squared l2 penalty.
kernel : string, optional (default='rbf')
Specifies the kernel type to be used in the algorithm.
It must be one of 'linear', 'poly', 'rbf', 'sigmoid', 'precomputed' or
a callable.
If none is given, 'rbf' will be used. If a callable is given it is
used to pre-compute the kernel matrix from data matrices; that matrix
should be an array of shape ``(n_samples, n_samples)``.
degree : int, optional (default=3)
Degree of the polynomial kernel function ('poly').
Ignored by all other kernels.
gamma : {'scale', 'auto'} or float, optional (default='scale')
Kernel coefficient for 'rbf', 'poly' and 'sigmoid'.
- if ``gamma='scale'`` (default) is passed then it uses
1 / (n_features * X.var()) as value of gamma,
- if 'auto', uses 1 / n_features.
.. versionchanged:: 0.22
The default value of ``gamma`` changed from 'auto' to 'scale'.
coef0 : float, optional (default=0.0)
Independent term in kernel function.
It is only significant in 'poly' and 'sigmoid'.
shrinking : boolean, optional (default=True)
Whether to use the shrinking heuristic.
probability : boolean, optional (default=False)
Whether to enable probability estimates. This must be enabled prior
to calling `fit`, will slow down that method as it internally uses
5-fold cross-validation, and `predict_proba` may be inconsistent with
`predict`. Read more in the :ref:`User Guide <scores_probabilities>`.
tol : float, optional (default=1e-3)
Tolerance for stopping criterion.
cache_size : float, optional
Specify the size of the kernel cache (in MB).
class_weight : {dict, 'balanced'}, optional
Set the parameter C of class i to class_weight[i]*C for
SVC. If not given, all classes are supposed to have
weight one.
The "balanced" mode uses the values of y to automatically adjust
weights inversely proportional to class frequencies in the input data
as ``n_samples / (n_classes * np.bincount(y))``
verbose : bool, default: False
Enable verbose output. Note that this setting takes advantage of a
per-process runtime setting in libsvm that, if enabled, may not work
properly in a multithreaded context.
max_iter : int, optional (default=-1)
Hard limit on iterations within solver, or -1 for no limit.
decision_function_shape : 'ovo', 'ovr', default='ovr'
Whether to return a one-vs-rest ('ovr') decision function of shape
(n_samples, n_classes) as all other classifiers, or the original
one-vs-one ('ovo') decision function of libsvm which has shape
(n_samples, n_classes * (n_classes - 1) / 2). However, one-vs-one
('ovo') is always used as multi-class strategy.
.. versionchanged:: 0.19
decision_function_shape is 'ovr' by default.
.. versionadded:: 0.17
*decision_function_shape='ovr'* is recommended.
.. versionchanged:: 0.17
Deprecated *decision_function_shape='ovo' and None*.
break_ties : bool, optional (default=False)
If true, ``decision_function_shape='ovr'``, and number of classes > 2,
:term:`predict` will break ties according to the confidence values of
:term:`decision_function`; otherwise the first class among the tied
classes is returned. Please note that breaking ties comes at a
relatively high computational cost compared to a simple predict.
.. versionadded:: 0.22
random_state : int, RandomState instance or None, optional (default=None)
The seed of the pseudo random number generator used when shuffling
the data for probability estimates. If int, random_state is the
seed used by the random number generator; If RandomState instance,
random_state is the random number generator; If None, the random
number generator is the RandomState instance used by `np.random`.
Attributes
----------
support_ : array-like of shape (n_SV)
Indices of support vectors.
support_vectors_ : array-like of shape (n_SV, n_features)
Support vectors.
n_support_ : array-like, dtype=int32, shape = [n_class]
Number of support vectors for each class.
dual_coef_ : array, shape = [n_class-1, n_SV]
Coefficients of the support vector in the decision function.
For multiclass, coefficient for all 1-vs-1 classifiers.
The layout of the coefficients in the multiclass case is somewhat
non-trivial. See the section about multi-class classification in the
SVM section of the User Guide for details.
coef_ : array, shape = [n_class * (n_class-1) / 2, n_features]
Weights assigned to the features (coefficients in the primal
problem). This is only available in the case of a linear kernel.
`coef_` is a readonly property derived from `dual_coef_` and
`support_vectors_`.
intercept_ : ndarray of shape (n_class * (n_class-1) / 2,)
Constants in decision function.
fit_status_ : int
0 if correctly fitted, 1 otherwise (will raise warning)
classes_ : array of shape (n_classes,)
The classes labels.
probA_ : array, shape = [n_class * (n_class-1) / 2]
probB_ : array, shape = [n_class * (n_class-1) / 2]
If `probability=True`, it corresponds to the parameters learned in
Platt scaling to produce probability estimates from decision values.
If `probability=False`, it's an empty array. Platt scaling uses the
logistic function
``1 / (1 + exp(decision_value * probA_ + probB_))``
where ``probA_`` and ``probB_`` are learned from the dataset [2]_. For
more information on the multiclass case and training procedure see
section 8 of [1]_.
class_weight_ : ndarray of shape (n_class,)
Multipliers of parameter C for each class.
Computed based on the ``class_weight`` parameter.
shape_fit_ : tuple of int of shape (n_dimensions_of_X,)
Array dimensions of training vector ``X``.
Examples
--------
>>> import numpy as np
>>> X = np.array([[-1, -1], [-2, -1], [1, 1], [2, 1]])
>>> y = np.array([1, 1, 2, 2])
>>> from sklearn.svm import SVC
>>> clf = SVC(gamma='auto')
>>> clf.fit(X, y)
SVC(gamma='auto')
>>> print(clf.predict([[-0.8, -1]]))
[1]
See also
--------
SVR
Support Vector Machine for Regression implemented using libsvm.
LinearSVC
Scalable Linear Support Vector Machine for classification
implemented using liblinear. Check the See also section of
LinearSVC for more comparison element.
References
----------
.. [1] `LIBSVM: A Library for Support Vector Machines
<http://www.csie.ntu.edu.tw/~cjlin/papers/libsvm.pdf>`_
.. [2] `Platt, John (1999). "Probabilistic outputs for support vector
machines and comparison to regularizedlikelihood methods."
<http://citeseer.ist.psu.edu/viewdoc/summary?doi=10.1.1.41.1639>`_
"""
_impl = 'c_svc'
def __init__(self, C=1.0, kernel='rbf', degree=3, gamma='scale',
coef0=0.0, shrinking=True, probability=False,
tol=1e-3, cache_size=200, class_weight=None,
verbose=False, max_iter=-1, decision_function_shape='ovr',
break_ties=False,
random_state=None):
super().__init__(
kernel=kernel, degree=degree, gamma=gamma,
coef0=coef0, tol=tol, C=C, nu=0., shrinking=shrinking,
probability=probability, cache_size=cache_size,
class_weight=class_weight, verbose=verbose, max_iter=max_iter,
decision_function_shape=decision_function_shape,
break_ties=break_ties,
random_state=random_state)
class NuSVC(BaseSVC):
"""Nu-Support Vector Classification.
Similar to SVC but uses a parameter to control the number of support
vectors.
The implementation is based on libsvm.
Read more in the :ref:`User Guide <svm_classification>`.
Parameters
----------
nu : float, optional (default=0.5)
An upper bound on the fraction of training errors and a lower
bound of the fraction of support vectors. Should be in the
interval (0, 1].
kernel : string, optional (default='rbf')
Specifies the kernel type to be used in the algorithm.
It must be one of 'linear', 'poly', 'rbf', 'sigmoid', 'precomputed' or
a callable.
If none is given, 'rbf' will be used. If a callable is given it is
used to precompute the kernel matrix.
degree : int, optional (default=3)
Degree of the polynomial kernel function ('poly').
Ignored by all other kernels.
gamma : {'scale', 'auto'} or float, optional (default='scale')
Kernel coefficient for 'rbf', 'poly' and 'sigmoid'.
- if ``gamma='scale'`` (default) is passed then it uses
1 / (n_features * X.var()) as value of gamma,
- if 'auto', uses 1 / n_features.
.. versionchanged:: 0.22
The default value of ``gamma`` changed from 'auto' to 'scale'.
coef0 : float, optional (default=0.0)
Independent term in kernel function.
It is only significant in 'poly' and 'sigmoid'.
shrinking : boolean, optional (default=True)
Whether to use the shrinking heuristic.
probability : boolean, optional (default=False)
Whether to enable probability estimates. This must be enabled prior
to calling `fit`, will slow down that method as it internally uses
5-fold cross-validation, and `predict_proba` may be inconsistent with
`predict`. Read more in the :ref:`User Guide <scores_probabilities>`.
tol : float, optional (default=1e-3)
Tolerance for stopping criterion.
cache_size : float, optional
Specify the size of the kernel cache (in MB).
class_weight : {dict, 'balanced'}, optional
Set the parameter C of class i to class_weight[i]*C for
SVC. If not given, all classes are supposed to have
weight one. The "balanced" mode uses the values of y to automatically
adjust weights inversely proportional to class frequencies as
``n_samples / (n_classes * np.bincount(y))``
verbose : bool, default: False
Enable verbose output. Note that this setting takes advantage of a
per-process runtime setting in libsvm that, if enabled, may not work
properly in a multithreaded context.
max_iter : int, optional (default=-1)
Hard limit on iterations within solver, or -1 for no limit.
decision_function_shape : 'ovo', 'ovr', default='ovr'
Whether to return a one-vs-rest ('ovr') decision function of shape
(n_samples, n_classes) as all other classifiers, or the original
one-vs-one ('ovo') decision function of libsvm which has shape
(n_samples, n_classes * (n_classes - 1) / 2).
.. versionchanged:: 0.19
decision_function_shape is 'ovr' by default.
.. versionadded:: 0.17
*decision_function_shape='ovr'* is recommended.
.. versionchanged:: 0.17
Deprecated *decision_function_shape='ovo' and None*.
break_ties : bool, optional (default=False)
If true, ``decision_function_shape='ovr'``, and number of classes > 2,
:term:`predict` will break ties according to the confidence values of
:term:`decision_function`; otherwise the first class among the tied
classes is returned. Please note that breaking ties comes at a
relatively high computational cost compared to a simple predict.
.. versionadded:: 0.22
random_state : int, RandomState instance or None, optional (default=None)
The seed of the pseudo random number generator used when shuffling
the data for probability estimates. If int, random_state is the seed
used by the random number generator; If RandomState instance,
random_state is the random number generator; If None, the random
number generator is the RandomState instance used by `np.random`.
Attributes
----------
support_ : array-like of shape (n_SV)
Indices of support vectors.
support_vectors_ : array-like of shape (n_SV, n_features)
Support vectors.
n_support_ : array-like, dtype=int32, shape = [n_class]
Number of support vectors for each class.
dual_coef_ : array, shape = [n_class-1, n_SV]
Coefficients of the support vector in the decision function.
For multiclass, coefficient for all 1-vs-1 classifiers.
The layout of the coefficients in the multiclass case is somewhat
non-trivial. See the section about multi-class classification in
the SVM section of the User Guide for details.
coef_ : array, shape = [n_class * (n_class-1) / 2, n_features]
Weights assigned to the features (coefficients in the primal
problem). This is only available in the case of a linear kernel.
`coef_` is readonly property derived from `dual_coef_` and
`support_vectors_`.
intercept_ : ndarray of shape (n_class * (n_class-1) / 2,)
Constants in decision function.
classes_ : array of shape (n_classes,)
The unique classes labels.
fit_status_ : int
0 if correctly fitted, 1 if the algorithm did not converge.
probA_ : ndarray, shape of (n_class * (n_class-1) / 2,)
probB_ : ndarray of shape (n_class * (n_class-1) / 2,)
If `probability=True`, it corresponds to the parameters learned in
Platt scaling to produce probability estimates from decision values.
If `probability=False`, it's an empty array. Platt scaling uses the
logistic function
``1 / (1 + exp(decision_value * probA_ + probB_))``
where ``probA_`` and ``probB_`` are learned from the dataset [2]_. For
more information on the multiclass case and training procedure see
section 8 of [1]_.
class_weight_ : ndarray of shape (n_class,)
Multipliers of parameter C of each class.
Computed based on the ``class_weight`` parameter.
shape_fit_ : tuple of int of shape (n_dimensions_of_X,)
Array dimensions of training vector ``X``.
Examples
--------
>>> import numpy as np
>>> X = np.array([[-1, -1], [-2, -1], [1, 1], [2, 1]])
>>> y = np.array([1, 1, 2, 2])
>>> from sklearn.svm import NuSVC
>>> clf = NuSVC()
>>> clf.fit(X, y)
NuSVC()
>>> print(clf.predict([[-0.8, -1]]))
[1]
See also
--------
SVC
Support Vector Machine for classification using libsvm.
LinearSVC
Scalable linear Support Vector Machine for classification using
liblinear.
References
----------
.. [1] `LIBSVM: A Library for Support Vector Machines
<http://www.csie.ntu.edu.tw/~cjlin/papers/libsvm.pdf>`_
.. [2] `Platt, John (1999). "Probabilistic outputs for support vector
machines and comparison to regularizedlikelihood methods."
<http://citeseer.ist.psu.edu/viewdoc/summary?doi=10.1.1.41.1639>`_
"""
_impl = 'nu_svc'
def __init__(self, nu=0.5, kernel='rbf', degree=3, gamma='scale',
coef0=0.0, shrinking=True, probability=False, tol=1e-3,
cache_size=200, class_weight=None, verbose=False, max_iter=-1,
decision_function_shape='ovr', break_ties=False,
random_state=None):
super().__init__(
kernel=kernel, degree=degree, gamma=gamma,
coef0=coef0, tol=tol, C=0., nu=nu, shrinking=shrinking,
probability=probability, cache_size=cache_size,
class_weight=class_weight, verbose=verbose, max_iter=max_iter,
decision_function_shape=decision_function_shape,
break_ties=break_ties,
random_state=random_state)
class SVR(RegressorMixin, BaseLibSVM):
"""Epsilon-Support Vector Regression.
The free parameters in the model are C and epsilon.
The implementation is based on libsvm. The fit time complexity
is more than quadratic with the number of samples which makes it hard
to scale to datasets with more than a couple of 10000 samples. For large
datasets consider using :class:`sklearn.svm.LinearSVR` or
:class:`sklearn.linear_model.SGDRegressor` instead, possibly after a
:class:`sklearn.kernel_approximation.Nystroem` transformer.
Read more in the :ref:`User Guide <svm_regression>`.
Parameters
----------
kernel : string, optional (default='rbf')
Specifies the kernel type to be used in the algorithm.
It must be one of 'linear', 'poly', 'rbf', 'sigmoid', 'precomputed' or
a callable.
If none is given, 'rbf' will be used. If a callable is given it is
used to precompute the kernel matrix.
degree : int, optional (default=3)
Degree of the polynomial kernel function ('poly').
Ignored by all other kernels.
gamma : {'scale', 'auto'} or float, optional (default='scale')
Kernel coefficient for 'rbf', 'poly' and 'sigmoid'.
- if ``gamma='scale'`` (default) is passed then it uses
1 / (n_features * X.var()) as value of gamma,
- if 'auto', uses 1 / n_features.
.. versionchanged:: 0.22
The default value of ``gamma`` changed from 'auto' to 'scale'.
coef0 : float, optional (default=0.0)
Independent term in kernel function.
It is only significant in 'poly' and 'sigmoid'.
tol : float, optional (default=1e-3)
Tolerance for stopping criterion.
C : float, optional (default=1.0)
Regularization parameter. The strength of the regularization is
inversely proportional to C. Must be strictly positive.
The penalty is a squared l2 penalty.
epsilon : float, optional (default=0.1)
Epsilon in the epsilon-SVR model. It specifies the epsilon-tube
within which no penalty is associated in the training loss function
with points predicted within a distance epsilon from the actual
value.
shrinking : boolean, optional (default=True)
Whether to use the shrinking heuristic.
cache_size : float, optional
Specify the size of the kernel cache (in MB).
verbose : bool, default: False
Enable verbose output. Note that this setting takes advantage of a
per-process runtime setting in libsvm that, if enabled, may not work
properly in a multithreaded context.
max_iter : int, optional (default=-1)
Hard limit on iterations within solver, or -1 for no limit.
Attributes
----------
support_ : array-like of shape (n_SV)
Indices of support vectors.
support_vectors_ : array-like of shape (n_SV, n_features)
Support vectors.
dual_coef_ : array, shape = [1, n_SV]
Coefficients of the support vector in the decision function.
coef_ : array, shape = [1, n_features]
Weights assigned to the features (coefficients in the primal
problem). This is only available in the case of a linear kernel.
`coef_` is readonly property derived from `dual_coef_` and
`support_vectors_`.
fit_status_ : int
0 if correctly fitted, 1 otherwise (will raise warning)
intercept_ : array, shape = [1]
Constants in decision function.
Examples
--------
>>> from sklearn.svm import SVR
>>> import numpy as np
>>> n_samples, n_features = 10, 5
>>> rng = np.random.RandomState(0)
>>> y = rng.randn(n_samples)
>>> X = rng.randn(n_samples, n_features)
>>> clf = SVR(C=1.0, epsilon=0.2)
>>> clf.fit(X, y)
SVR(epsilon=0.2)
See also
--------
NuSVR
Support Vector Machine for regression implemented using libsvm
using a parameter to control the number of support vectors.
LinearSVR
Scalable Linear Support Vector Machine for regression
implemented using liblinear.
Notes
-----
**References:**
`LIBSVM: A Library for Support Vector Machines
<http://www.csie.ntu.edu.tw/~cjlin/papers/libsvm.pdf>`__
"""
_impl = 'epsilon_svr'
def __init__(self, kernel='rbf', degree=3, gamma='scale',
coef0=0.0, tol=1e-3, C=1.0, epsilon=0.1, shrinking=True,
cache_size=200, verbose=False, max_iter=-1):
super().__init__(
kernel=kernel, degree=degree, gamma=gamma,
coef0=coef0, tol=tol, C=C, nu=0., epsilon=epsilon, verbose=verbose,
shrinking=shrinking, probability=False, cache_size=cache_size,
class_weight=None, max_iter=max_iter, random_state=None)
class NuSVR(RegressorMixin, BaseLibSVM):
"""Nu Support Vector Regression.
Similar to NuSVC, for regression, uses a parameter nu to control
the number of support vectors. However, unlike NuSVC, where nu
replaces C, here nu replaces the parameter epsilon of epsilon-SVR.
The implementation is based on libsvm.
Read more in the :ref:`User Guide <svm_regression>`.
Parameters
----------
nu : float, optional
An upper bound on the fraction of training errors and a lower bound of
the fraction of support vectors. Should be in the interval (0, 1]. By
default 0.5 will be taken.
C : float, optional (default=1.0)
Penalty parameter C of the error term.
kernel : string, optional (default='rbf')
Specifies the kernel type to be used in the algorithm.
It must be one of 'linear', 'poly', 'rbf', 'sigmoid', 'precomputed' or
a callable.
If none is given, 'rbf' will be used. If a callable is given it is
used to precompute the kernel matrix.
degree : int, optional (default=3)
Degree of the polynomial kernel function ('poly').
Ignored by all other kernels.
gamma : {'scale', 'auto'} or float, optional (default='scale')
Kernel coefficient for 'rbf', 'poly' and 'sigmoid'.
- if ``gamma='scale'`` (default) is passed then it uses
1 / (n_features * X.var()) as value of gamma,
- if 'auto', uses 1 / n_features.
.. versionchanged:: 0.22
The default value of ``gamma`` changed from 'auto' to 'scale'.
coef0 : float, optional (default=0.0)
Independent term in kernel function.
It is only significant in 'poly' and 'sigmoid'.
shrinking : boolean, optional (default=True)
Whether to use the shrinking heuristic.
tol : float, optional (default=1e-3)
Tolerance for stopping criterion.
cache_size : float, optional
Specify the size of the kernel cache (in MB).
verbose : bool, default: False
Enable verbose output. Note that this setting takes advantage of a
per-process runtime setting in libsvm that, if enabled, may not work
properly in a multithreaded context.
max_iter : int, optional (default=-1)
Hard limit on iterations within solver, or -1 for no limit.
Attributes
----------
support_ : array-like of shape (n_SV)
Indices of support vectors.
support_vectors_ : array-like of shape (n_SV, n_features)
Support vectors.
dual_coef_ : array, shape = [1, n_SV]
Coefficients of the support vector in the decision function.
coef_ : array, shape = [1, n_features]
Weights assigned to the features (coefficients in the primal
problem). This is only available in the case of a linear kernel.
`coef_` is readonly property derived from `dual_coef_` and
`support_vectors_`.
intercept_ : array, shape = [1]
Constants in decision function.
Examples
--------
>>> from sklearn.svm import NuSVR
>>> import numpy as np
>>> n_samples, n_features = 10, 5
>>> np.random.seed(0)
>>> y = np.random.randn(n_samples)
>>> X = np.random.randn(n_samples, n_features)
>>> clf = NuSVR(C=1.0, nu=0.1)
>>> clf.fit(X, y)
NuSVR(nu=0.1)
See also
--------
NuSVC
Support Vector Machine for classification implemented with libsvm
with a parameter to control the number of support vectors.
SVR
epsilon Support Vector Machine for regression implemented with libsvm.
Notes
-----
**References:**
`LIBSVM: A Library for Support Vector Machines
<http://www.csie.ntu.edu.tw/~cjlin/papers/libsvm.pdf>`__
"""
_impl = 'nu_svr'
def __init__(self, nu=0.5, C=1.0, kernel='rbf', degree=3,
gamma='scale', coef0=0.0, shrinking=True,
tol=1e-3, cache_size=200, verbose=False, max_iter=-1):
super().__init__(
kernel=kernel, degree=degree, gamma=gamma, coef0=coef0,
tol=tol, C=C, nu=nu, epsilon=0., shrinking=shrinking,
probability=False, cache_size=cache_size, class_weight=None,
verbose=verbose, max_iter=max_iter, random_state=None)
class OneClassSVM(OutlierMixin, BaseLibSVM):
"""Unsupervised Outlier Detection.
Estimate the support of a high-dimensional distribution.
The implementation is based on libsvm.
Read more in the :ref:`User Guide <outlier_detection>`.
Parameters
----------
kernel : string, optional (default='rbf')
Specifies the kernel type to be used in the algorithm.
It must be one of 'linear', 'poly', 'rbf', 'sigmoid', 'precomputed' or
a callable.
If none is given, 'rbf' will be used. If a callable is given it is
used to precompute the kernel matrix.
degree : int, optional (default=3)
Degree of the polynomial kernel function ('poly').
Ignored by all other kernels.
gamma : {'scale', 'auto'} or float, optional (default='scale')
Kernel coefficient for 'rbf', 'poly' and 'sigmoid'.
- if ``gamma='scale'`` (default) is passed then it uses
1 / (n_features * X.var()) as value of gamma,
- if 'auto', uses 1 / n_features.
.. versionchanged:: 0.22
The default value of ``gamma`` changed from 'auto' to 'scale'.
coef0 : float, optional (default=0.0)
Independent term in kernel function.
It is only significant in 'poly' and 'sigmoid'.
tol : float, optional
Tolerance for stopping criterion.
nu : float, optional
An upper bound on the fraction of training
errors and a lower bound of the fraction of support
vectors. Should be in the interval (0, 1]. By default 0.5
will be taken.
shrinking : boolean, optional
Whether to use the shrinking heuristic.
cache_size : float, optional
Specify the size of the kernel cache (in MB).
verbose : bool, default: False
Enable verbose output. Note that this setting takes advantage of a
per-process runtime setting in libsvm that, if enabled, may not work
properly in a multithreaded context.
max_iter : int, optional (default=-1)
Hard limit on iterations within solver, or -1 for no limit.
Attributes
----------
support_ : array-like of shape (n_SV)
Indices of support vectors.
support_vectors_ : array-like of shape (n_SV, n_features)
Support vectors.
dual_coef_ : array, shape = [1, n_SV]
Coefficients of the support vectors in the decision function.
coef_ : array, shape = [1, n_features]
Weights assigned to the features (coefficients in the primal
problem). This is only available in the case of a linear kernel.
`coef_` is readonly property derived from `dual_coef_` and
`support_vectors_`
intercept_ : array, shape = [1,]
Constant in the decision function.
offset_ : float
Offset used to define the decision function from the raw scores.
We have the relation: decision_function = score_samples - `offset_`.
The offset is the opposite of `intercept_` and is provided for
consistency with other outlier detection algorithms.
fit_status_ : int
0 if correctly fitted, 1 otherwise (will raise warning)
Examples
--------
>>> from sklearn.svm import OneClassSVM
>>> X = [[0], [0.44], [0.45], [0.46], [1]]
>>> clf = OneClassSVM(gamma='auto').fit(X)
>>> clf.predict(X)
array([-1, 1, 1, 1, -1])
>>> clf.score_samples(X) # doctest: +ELLIPSIS
array([1.7798..., 2.0547..., 2.0556..., 2.0561..., 1.7332...])
"""
_impl = 'one_class'
def __init__(self, kernel='rbf', degree=3, gamma='scale',
coef0=0.0, tol=1e-3, nu=0.5, shrinking=True, cache_size=200,
verbose=False, max_iter=-1):
super().__init__(
kernel, degree, gamma, coef0, tol, 0., nu, 0.,
shrinking, False, cache_size, None, verbose, max_iter,
random_state=None)
def fit(self, X, y=None, sample_weight=None, **params):
"""
Detects the soft boundary of the set of samples X.
Parameters
----------
X : {array-like, sparse matrix}, shape (n_samples, n_features)
Set of samples, where n_samples is the number of samples and
n_features is the number of features.
sample_weight : array-like, shape (n_samples,)
Per-sample weights. Rescale C per sample. Higher weights
force the classifier to put more emphasis on these points.
y : Ignored
not used, present for API consistency by convention.
Returns
-------
self : object
Notes
-----
If X is not a C-ordered contiguous array it is copied.
"""
super().fit(X, np.ones(_num_samples(X)),
sample_weight=sample_weight, **params)
self.offset_ = -self._intercept_
return self
def decision_function(self, X):
"""Signed distance to the separating hyperplane.
Signed distance is positive for an inlier and negative for an outlier.
Parameters
----------
X : array-like, shape (n_samples, n_features)
Returns
-------
dec : array-like, shape (n_samples,)
Returns the decision function of the samples.
"""
dec = self._decision_function(X).ravel()
return dec
def score_samples(self, X):
"""Raw scoring function of the samples.
Parameters
----------
X : array-like, shape (n_samples, n_features)
Returns
-------
score_samples : array-like, shape (n_samples,)
Returns the (unshifted) scoring function of the samples.
"""
return self.decision_function(X) + self.offset_
def predict(self, X):
"""
Perform classification on samples in X.
For a one-class model, +1 or -1 is returned.
Parameters
----------
X : {array-like, sparse matrix}, shape (n_samples, n_features)
For kernel="precomputed", the expected shape of X is
[n_samples_test, n_samples_train]
Returns
-------
y_pred : array, shape (n_samples,)
Class labels for samples in X.
"""
y = super().predict(X)
return np.asarray(y, dtype=np.intp)