"""
The :mod:`sklearn.cross_validation` module includes utilities for cross-
validation and performance evaluation.
"""
# Author: Alexandre Gramfort <alexandre.gramfort@inria.fr>,
# Gael Varoquaux <gael.varoquaux@normalesup.org>,
# Olivier Grisel <olivier.grisel@ensta.org>
# License: BSD 3 clause
from __future__ import print_function
from __future__ import division
import warnings
from itertools import chain, combinations
from math import ceil, floor, factorial
import numbers
import time
from abc import ABCMeta, abstractmethod
import numpy as np
import scipy.sparse as sp
from .base import is_classifier, clone
from .utils import indexable, check_random_state, safe_indexing
from .utils.validation import _num_samples, check_array
from .utils.multiclass import type_of_target
from .externals.joblib import Parallel, delayed, logger
from .externals.six import with_metaclass
from .externals.six.moves import zip
from .metrics.scorer import check_scoring
__all__ = ['Bootstrap',
'KFold',
'LeaveOneLabelOut',
'LeaveOneOut',
'LeavePLabelOut',
'LeavePOut',
'ShuffleSplit',
'StratifiedKFold',
'StratifiedShuffleSplit',
'check_cv',
'cross_val_score',
'permutation_test_score',
'train_test_split']
class _PartitionIterator(with_metaclass(ABCMeta)):
"""Base class for CV iterators where train_mask = ~test_mask
Implementations must define `_iter_test_masks` or `_iter_test_indices`.
Parameters
----------
n : int
Total number of elements in dataset.
"""
def __init__(self, n, indices=None):
if indices is None:
indices = True
else:
warnings.warn("The indices parameter is deprecated and will be "
"removed (assumed True) in 0.17", DeprecationWarning,
stacklevel=1)
if abs(n - int(n)) >= np.finfo('f').eps:
raise ValueError("n must be an integer")
self.n = int(n)
self._indices = indices
@property
def indices(self):
warnings.warn("The indices attribute is deprecated and will be "
"removed (assumed True) in 0.17", DeprecationWarning,
stacklevel=1)
return self._indices
def __iter__(self):
indices = self._indices
if indices:
ind = np.arange(self.n)
for test_index in self._iter_test_masks():
train_index = np.logical_not(test_index)
if indices:
train_index = ind[train_index]
test_index = ind[test_index]
yield train_index, test_index
# Since subclasses must implement either _iter_test_masks or
# _iter_test_indices, neither can be abstract.
def _iter_test_masks(self):
"""Generates boolean masks corresponding to test sets.
By default, delegates to _iter_test_indices()
"""
for test_index in self._iter_test_indices():
test_mask = self._empty_mask()
test_mask[test_index] = True
yield test_mask
def _iter_test_indices(self):
"""Generates integer indices corresponding to test sets."""
raise NotImplementedError
def _empty_mask(self):
return np.zeros(self.n, dtype=np.bool)
class LeaveOneOut(_PartitionIterator):
"""Leave-One-Out cross validation iterator.
Provides train/test indices to split data in train test sets. Each
sample is used once as a test set (singleton) while the remaining
samples form the training set.
Note: ``LeaveOneOut(n)`` is equivalent to ``KFold(n, n_folds=n)`` and
``LeavePOut(n, p=1)``.
Due to the high number of test sets (which is the same as the
number of samples) this cross validation method can be very costly.
For large datasets one should favor KFold, StratifiedKFold or
ShuffleSplit.
Parameters
----------
n : int
Total number of elements in dataset.
Examples
--------
>>> from sklearn import cross_validation
>>> X = np.array([[1, 2], [3, 4]])
>>> y = np.array([1, 2])
>>> loo = cross_validation.LeaveOneOut(2)
>>> len(loo)
2
>>> print(loo)
sklearn.cross_validation.LeaveOneOut(n=2)
>>> for train_index, test_index in loo:
... print("TRAIN:", train_index, "TEST:", test_index)
... X_train, X_test = X[train_index], X[test_index]
... y_train, y_test = y[train_index], y[test_index]
... print(X_train, X_test, y_train, y_test)
TRAIN: [1] TEST: [0]
[[3 4]] [[1 2]] [2] [1]
TRAIN: [0] TEST: [1]
[[1 2]] [[3 4]] [1] [2]
See also
--------
LeaveOneLabelOut for splitting the data according to explicit,
domain-specific stratification of the dataset.
"""
def _iter_test_indices(self):
return range(self.n)
def __repr__(self):
return '%s.%s(n=%i)' % (
self.__class__.__module__,
self.__class__.__name__,
self.n,
)
def __len__(self):
return self.n
class LeavePOut(_PartitionIterator):
"""Leave-P-Out cross validation iterator
Provides train/test indices to split data in train test sets. This results
in testing on all distinct samples of size p, while the remaining n - p
samples form the training set in each iteration.
Note: ``LeavePOut(n, p)`` is NOT equivalent to ``KFold(n, n_folds=n // p)``
which creates non-overlapping test sets.
Due to the high number of iterations which grows combinatorically with the
number of samples this cross validation method can be very costly. For
large datasets one should favor KFold, StratifiedKFold or ShuffleSplit.
Parameters
----------
n : int
Total number of elements in dataset.
p : int
Size of the test sets.
Examples
--------
>>> from sklearn import cross_validation
>>> X = np.array([[1, 2], [3, 4], [5, 6], [7, 8]])
>>> y = np.array([1, 2, 3, 4])
>>> lpo = cross_validation.LeavePOut(4, 2)
>>> len(lpo)
6
>>> print(lpo)
sklearn.cross_validation.LeavePOut(n=4, p=2)
>>> for train_index, test_index in lpo:
... print("TRAIN:", train_index, "TEST:", test_index)
... X_train, X_test = X[train_index], X[test_index]
... y_train, y_test = y[train_index], y[test_index]
TRAIN: [2 3] TEST: [0 1]
TRAIN: [1 3] TEST: [0 2]
TRAIN: [1 2] TEST: [0 3]
TRAIN: [0 3] TEST: [1 2]
TRAIN: [0 2] TEST: [1 3]
TRAIN: [0 1] TEST: [2 3]
"""
def __init__(self, n, p, indices=None):
super(LeavePOut, self).__init__(n, indices)
self.p = p
def _iter_test_indices(self):
for comb in combinations(range(self.n), self.p):
yield np.array(comb)
def __repr__(self):
return '%s.%s(n=%i, p=%i)' % (
self.__class__.__module__,
self.__class__.__name__,
self.n,
self.p,
)
def __len__(self):
return int(factorial(self.n) / factorial(self.n - self.p)
/ factorial(self.p))
class _BaseKFold(with_metaclass(ABCMeta, _PartitionIterator)):
"""Base class to validate KFold approaches"""
@abstractmethod
def __init__(self, n, n_folds, indices, shuffle, random_state):
super(_BaseKFold, self).__init__(n, indices)
if abs(n_folds - int(n_folds)) >= np.finfo('f').eps:
raise ValueError("n_folds must be an integer")
self.n_folds = n_folds = int(n_folds)
if n_folds <= 1:
raise ValueError(
"k-fold cross validation requires at least one"
" train / test split by setting n_folds=2 or more,"
" got n_folds={0}.".format(n_folds))
if n_folds > self.n:
raise ValueError(
("Cannot have number of folds n_folds={0} greater"
" than the number of samples: {1}.").format(n_folds, n))
if not isinstance(shuffle, bool):
raise TypeError("shuffle must be True or False;"
" got {0}".format(shuffle))
self.shuffle = shuffle
self.random_state = random_state
class KFold(_BaseKFold):
"""K-Folds cross validation iterator.
Provides train/test indices to split data in train test sets. Split
dataset into k consecutive folds (without shuffling).
Each fold is then used a validation set once while the k - 1 remaining
fold form the training set.
Parameters
----------
n : int
Total number of elements.
n_folds : int, default=3
Number of folds. Must be at least 2.
shuffle : boolean, optional
Whether to shuffle the data before splitting into batches.
random_state : None, int or RandomState
Pseudo-random number generator state used for random
sampling. If None, use default numpy RNG for shuffling
Examples
--------
>>> from sklearn import cross_validation
>>> X = np.array([[1, 2], [3, 4], [1, 2], [3, 4]])
>>> y = np.array([1, 2, 3, 4])
>>> kf = cross_validation.KFold(4, n_folds=2)
>>> len(kf)
2
>>> print(kf) # doctest: +NORMALIZE_WHITESPACE
sklearn.cross_validation.KFold(n=4, n_folds=2, shuffle=False,
random_state=None)
>>> for train_index, test_index in kf:
... print("TRAIN:", train_index, "TEST:", test_index)
... X_train, X_test = X[train_index], X[test_index]
... y_train, y_test = y[train_index], y[test_index]
TRAIN: [2 3] TEST: [0 1]
TRAIN: [0 1] TEST: [2 3]
Notes
-----
The first n % n_folds folds have size n // n_folds + 1, other folds have
size n // n_folds.
See also
--------
StratifiedKFold: take label information into account to avoid building
folds with imbalanced class distributions (for binary or multiclass
classification tasks).
"""
def __init__(self, n, n_folds=3, indices=None, shuffle=False,
random_state=None):
super(KFold, self).__init__(n, n_folds, indices, shuffle, random_state)
self.idxs = np.arange(n)
if shuffle:
rng = check_random_state(self.random_state)
rng.shuffle(self.idxs)
def _iter_test_indices(self):
n = self.n
n_folds = self.n_folds
fold_sizes = (n // n_folds) * np.ones(n_folds, dtype=np.int)
fold_sizes[:n % n_folds] += 1
current = 0
for fold_size in fold_sizes:
start, stop = current, current + fold_size
yield self.idxs[start:stop]
current = stop
def __repr__(self):
return '%s.%s(n=%i, n_folds=%i, shuffle=%s, random_state=%s)' % (
self.__class__.__module__,
self.__class__.__name__,
self.n,
self.n_folds,
self.shuffle,
self.random_state,
)
def __len__(self):
return self.n_folds
class StratifiedKFold(_BaseKFold):
"""Stratified K-Folds cross validation iterator
Provides train/test indices to split data in train test sets.
This cross-validation object is a variation of KFold that
returns stratified folds. The folds are made by preserving
the percentage of samples for each class.
Parameters
----------
y : array-like, [n_samples]
Samples to split in K folds.
n_folds : int, default=3
Number of folds. Must be at least 2.
shuffle : boolean, optional
Whether to shuffle each stratification of the data before splitting
into batches.
random_state : None, int or RandomState
Pseudo-random number generator state used for random
sampling. If None, use default numpy RNG for shuffling
Examples
--------
>>> from sklearn import cross_validation
>>> X = np.array([[1, 2], [3, 4], [1, 2], [3, 4]])
>>> y = np.array([0, 0, 1, 1])
>>> skf = cross_validation.StratifiedKFold(y, n_folds=2)
>>> len(skf)
2
>>> print(skf) # doctest: +NORMALIZE_WHITESPACE
sklearn.cross_validation.StratifiedKFold(labels=[0 0 1 1], n_folds=2,
shuffle=False, random_state=None)
>>> for train_index, test_index in skf:
... print("TRAIN:", train_index, "TEST:", test_index)
... X_train, X_test = X[train_index], X[test_index]
... y_train, y_test = y[train_index], y[test_index]
TRAIN: [1 3] TEST: [0 2]
TRAIN: [0 2] TEST: [1 3]
Notes
-----
All the folds have size trunc(n_samples / n_folds), the last one has the
complementary.
"""
def __init__(self, y, n_folds=3, indices=None, shuffle=False,
random_state=None):
super(StratifiedKFold, self).__init__(
len(y), n_folds, indices, shuffle, random_state)
y = np.asarray(y)
n_samples = y.shape[0]
unique_labels, y_inversed = np.unique(y, return_inverse=True)
label_counts = np.bincount(y_inversed)
min_labels = np.min(label_counts)
if self.n_folds > min_labels:
warnings.warn(("The least populated class in y has only %d"
" members, which is too few. The minimum"
" number of labels for any class cannot"
" be less than n_folds=%d."
% (min_labels, self.n_folds)), Warning)
# don't want to use the same seed in each label's shuffle
if self.shuffle:
rng = check_random_state(self.random_state)
else:
rng = self.random_state
# pre-assign each sample to a test fold index using individual KFold
# splitting strategies for each label so as to respect the
# balance of labels
per_label_cvs = [
KFold(max(c, self.n_folds), self.n_folds, shuffle=self.shuffle,
random_state=rng) for c in label_counts]
test_folds = np.zeros(n_samples, dtype=np.int)
for test_fold_idx, per_label_splits in enumerate(zip(*per_label_cvs)):
for label, (_, test_split) in zip(unique_labels, per_label_splits):
label_test_folds = test_folds[y == label]
# the test split can be too big because we used
# KFold(max(c, self.n_folds), self.n_folds) instead of
# KFold(c, self.n_folds) to make it possible to not crash even
# if the data is not 100% stratifiable for all the labels
# (we use a warning instead of raising an exception)
# If this is the case, let's trim it:
test_split = test_split[test_split < len(label_test_folds)]
label_test_folds[test_split] = test_fold_idx
test_folds[y == label] = label_test_folds
self.test_folds = test_folds
self.y = y
def _iter_test_masks(self):
for i in range(self.n_folds):
yield self.test_folds == i
def __repr__(self):
return '%s.%s(labels=%s, n_folds=%i, shuffle=%s, random_state=%s)' % (
self.__class__.__module__,
self.__class__.__name__,
self.y,
self.n_folds,
self.shuffle,
self.random_state,
)
def __len__(self):
return self.n_folds
class LeaveOneLabelOut(_PartitionIterator):
"""Leave-One-Label_Out cross-validation iterator
Provides train/test indices to split data according to a third-party
provided label. This label information can be used to encode arbitrary
domain specific stratifications of the samples as integers.
For instance the labels could be the year of collection of the samples
and thus allow for cross-validation against time-based splits.
Parameters
----------
labels : array-like of int with shape (n_samples,)
Arbitrary domain-specific stratification of the data to be used
to draw the splits.
Examples
--------
>>> from sklearn import cross_validation
>>> X = np.array([[1, 2], [3, 4], [5, 6], [7, 8]])
>>> y = np.array([1, 2, 1, 2])
>>> labels = np.array([1, 1, 2, 2])
>>> lol = cross_validation.LeaveOneLabelOut(labels)
>>> len(lol)
2
>>> print(lol)
sklearn.cross_validation.LeaveOneLabelOut(labels=[1 1 2 2])
>>> for train_index, test_index in lol:
... print("TRAIN:", train_index, "TEST:", test_index)
... X_train, X_test = X[train_index], X[test_index]
... y_train, y_test = y[train_index], y[test_index]
... print(X_train, X_test, y_train, y_test)
TRAIN: [2 3] TEST: [0 1]
[[5 6]
[7 8]] [[1 2]
[3 4]] [1 2] [1 2]
TRAIN: [0 1] TEST: [2 3]
[[1 2]
[3 4]] [[5 6]
[7 8]] [1 2] [1 2]
"""
def __init__(self, labels, indices=None):
super(LeaveOneLabelOut, self).__init__(len(labels), indices)
# We make a copy of labels to avoid side-effects during iteration
self.labels = np.array(labels, copy=True)
self.unique_labels = np.unique(labels)
self.n_unique_labels = len(self.unique_labels)
def _iter_test_masks(self):
for i in self.unique_labels:
yield self.labels == i
def __repr__(self):
return '%s.%s(labels=%s)' % (
self.__class__.__module__,
self.__class__.__name__,
self.labels,
)
def __len__(self):
return self.n_unique_labels
class LeavePLabelOut(_PartitionIterator):
"""Leave-P-Label_Out cross-validation iterator
Provides train/test indices to split data according to a third-party
provided label. This label information can be used to encode arbitrary
domain specific stratifications of the samples as integers.
For instance the labels could be the year of collection of the samples
and thus allow for cross-validation against time-based splits.
The difference between LeavePLabelOut and LeaveOneLabelOut is that
the former builds the test sets with all the samples assigned to
``p`` different values of the labels while the latter uses samples
all assigned the same labels.
Parameters
----------
labels : array-like of int with shape (n_samples,)
Arbitrary domain-specific stratification of the data to be used
to draw the splits.
p : int
Number of samples to leave out in the test split.
Examples
--------
>>> from sklearn import cross_validation
>>> X = np.array([[1, 2], [3, 4], [5, 6]])
>>> y = np.array([1, 2, 1])
>>> labels = np.array([1, 2, 3])
>>> lpl = cross_validation.LeavePLabelOut(labels, p=2)
>>> len(lpl)
3
>>> print(lpl)
sklearn.cross_validation.LeavePLabelOut(labels=[1 2 3], p=2)
>>> for train_index, test_index in lpl:
... print("TRAIN:", train_index, "TEST:", test_index)
... X_train, X_test = X[train_index], X[test_index]
... y_train, y_test = y[train_index], y[test_index]
... print(X_train, X_test, y_train, y_test)
TRAIN: [2] TEST: [0 1]
[[5 6]] [[1 2]
[3 4]] [1] [1 2]
TRAIN: [1] TEST: [0 2]
[[3 4]] [[1 2]
[5 6]] [2] [1 1]
TRAIN: [0] TEST: [1 2]
[[1 2]] [[3 4]
[5 6]] [1] [2 1]
"""
def __init__(self, labels, p, indices=None):
# We make a copy of labels to avoid side-effects during iteration
super(LeavePLabelOut, self).__init__(len(labels), indices)
self.labels = np.array(labels, copy=True)
self.unique_labels = np.unique(labels)
self.n_unique_labels = len(self.unique_labels)
self.p = p
def _iter_test_masks(self):
comb = combinations(range(self.n_unique_labels), self.p)
for idx in comb:
test_index = self._empty_mask()
idx = np.array(idx)
for l in self.unique_labels[idx]:
test_index[self.labels == l] = True
yield test_index
def __repr__(self):
return '%s.%s(labels=%s, p=%s)' % (
self.__class__.__module__,
self.__class__.__name__,
self.labels,
self.p,
)
def __len__(self):
return int(factorial(self.n_unique_labels) /
factorial(self.n_unique_labels - self.p) /
factorial(self.p))
class Bootstrap(object):
"""Random sampling with replacement cross-validation iterator
Provides train/test indices to split data in train test sets
while resampling the input n_iter times: each time a new
random split of the data is performed and then samples are drawn
(with replacement) on each side of the split to build the training
and test sets.
Note: contrary to other cross-validation strategies, bootstrapping
will allow some samples to occur several times in each splits. However
a sample that occurs in the train split will never occur in the test
split and vice-versa.
If you want each sample to occur at most once you should probably
use ShuffleSplit cross validation instead.
Parameters
----------
n : int
Total number of elements in the dataset.
n_iter : int (default is 3)
Number of bootstrapping iterations
train_size : int or float (default is 0.5)
If int, number of samples to include in the training split
(should be smaller than the total number of samples passed
in the dataset).
If float, should be between 0.0 and 1.0 and represent the
proportion of the dataset to include in the train split.
test_size : int or float or None (default is None)
If int, number of samples to include in the training set
(should be smaller than the total number of samples passed
in the dataset).
If float, should be between 0.0 and 1.0 and represent the
proportion of the dataset to include in the test split.
If None, n_test is set as the complement of n_train.
random_state : int or RandomState
Pseudo number generator state used for random sampling.
Examples
--------
>>> from sklearn import cross_validation
>>> bs = cross_validation.Bootstrap(9, random_state=0)
>>> len(bs)
3
>>> print(bs)
Bootstrap(9, n_iter=3, train_size=5, test_size=4, random_state=0)
>>> for train_index, test_index in bs:
... print("TRAIN:", train_index, "TEST:", test_index)
...
TRAIN: [1 8 7 7 8] TEST: [0 3 0 5]
TRAIN: [5 4 2 4 2] TEST: [6 7 1 0]
TRAIN: [4 7 0 1 1] TEST: [5 3 6 5]
See also
--------
ShuffleSplit: cross validation using random permutations.
"""
# Static marker to be able to introspect the CV type
indices = True
def __init__(self, n, n_iter=3, train_size=.5, test_size=None,
random_state=None, n_bootstraps=None):
# See, e.g., http://youtu.be/BzHz0J9a6k0?t=9m38s for a motivation
# behind this deprecation
warnings.warn("Bootstrap will no longer be supported as a " +
"cross-validation method as of version 0.15 and " +
"will be removed in 0.17", DeprecationWarning)
self.n = n
if n_bootstraps is not None: # pragma: no cover
warnings.warn("n_bootstraps was renamed to n_iter and will "
"be removed in 0.16.", DeprecationWarning)
n_iter = n_bootstraps
self.n_iter = n_iter
if (isinstance(train_size, numbers.Real) and train_size >= 0.0
and train_size <= 1.0):
self.train_size = int(ceil(train_size * n))
elif isinstance(train_size, numbers.Integral):
self.train_size = train_size
else:
raise ValueError("Invalid value for train_size: %r" %
train_size)
if self.train_size > n:
raise ValueError("train_size=%d should not be larger than n=%d" %
(self.train_size, n))
if isinstance(test_size, numbers.Real) and 0.0 <= test_size <= 1.0:
self.test_size = int(ceil(test_size * n))
elif isinstance(test_size, numbers.Integral):
self.test_size = test_size
elif test_size is None:
self.test_size = self.n - self.train_size
else:
raise ValueError("Invalid value for test_size: %r" % test_size)
if self.test_size > n - self.train_size:
raise ValueError(("test_size + train_size=%d, should not be " +
"larger than n=%d") %
(self.test_size + self.train_size, n))
self.random_state = random_state
def __iter__(self):
rng = check_random_state(self.random_state)
for i in range(self.n_iter):
# random partition
permutation = rng.permutation(self.n)
ind_train = permutation[:self.train_size]
ind_test = permutation[self.train_size:self.train_size
+ self.test_size]
# bootstrap in each split individually
train = rng.randint(0, self.train_size,
size=(self.train_size,))
test = rng.randint(0, self.test_size,
size=(self.test_size,))
yield ind_train[train], ind_test[test]
def __repr__(self):
return ('%s(%d, n_iter=%d, train_size=%d, test_size=%d, '
'random_state=%s)' % (
self.__class__.__name__,
self.n,
self.n_iter,
self.train_size,
self.test_size,
self.random_state,
))
def __len__(self):
return self.n_iter
class BaseShuffleSplit(with_metaclass(ABCMeta)):
"""Base class for ShuffleSplit and StratifiedShuffleSplit"""
def __init__(self, n, n_iter=10, test_size=0.1, train_size=None,
indices=None, random_state=None, n_iterations=None):
if indices is None:
indices = True
else:
warnings.warn("The indices parameter is deprecated and will be "
"removed (assumed True) in 0.17", DeprecationWarning)
self.n = n
self.n_iter = n_iter
if n_iterations is not None: # pragma: no cover
warnings.warn("n_iterations was renamed to n_iter for consistency "
" and will be removed in 0.16.")
self.n_iter = n_iterations
self.test_size = test_size
self.train_size = train_size
self.random_state = random_state
self._indices = indices
self.n_train, self.n_test = _validate_shuffle_split(n,
test_size,
train_size)
@property
def indices(self):
warnings.warn("The indices attribute is deprecated and will be "
"removed (assumed True) in 0.17", DeprecationWarning,
stacklevel=1)
return self._indices
def __iter__(self):
if self._indices:
for train, test in self._iter_indices():
yield train, test
return
for train, test in self._iter_indices():
train_m = np.zeros(self.n, dtype=bool)
test_m = np.zeros(self.n, dtype=bool)
train_m[train] = True
test_m[test] = True
yield train_m, test_m
@abstractmethod
def _iter_indices(self):
"""Generate (train, test) indices"""
class ShuffleSplit(BaseShuffleSplit):
"""Random permutation cross-validation iterator.
Yields indices to split data into training and test sets.
Note: contrary to other cross-validation strategies, random splits
do not guarantee that all folds will be different, although this is
still very likely for sizeable datasets.
Parameters
----------
n : int
Total number of elements in the dataset.
n_iter : int (default 10)
Number of re-shuffling & splitting iterations.
test_size : float (default 0.1), int, or None
If float, should be between 0.0 and 1.0 and represent the
proportion of the dataset to include in the test split. If
int, represents the absolute number of test samples. If None,
the value is automatically set to the complement of the train size.
train_size : float, int, or None (default is None)
If float, should be between 0.0 and 1.0 and represent the
proportion of the dataset to include in the train split. If
int, represents the absolute number of train samples. If None,
the value is automatically set to the complement of the test size.
random_state : int or RandomState
Pseudo-random number generator state used for random sampling.
Examples
--------
>>> from sklearn import cross_validation
>>> rs = cross_validation.ShuffleSplit(4, n_iter=3,
... test_size=.25, random_state=0)
>>> len(rs)
3
>>> print(rs)
... # doctest: +ELLIPSIS
ShuffleSplit(4, n_iter=3, test_size=0.25, ...)
>>> for train_index, test_index in rs:
... print("TRAIN:", train_index, "TEST:", test_index)
...
TRAIN: [3 1 0] TEST: [2]
TRAIN: [2 1 3] TEST: [0]
TRAIN: [0 2 1] TEST: [3]
>>> rs = cross_validation.ShuffleSplit(4, n_iter=3,
... train_size=0.5, test_size=.25, random_state=0)
>>> for train_index, test_index in rs:
... print("TRAIN:", train_index, "TEST:", test_index)
...
TRAIN: [3 1] TEST: [2]
TRAIN: [2 1] TEST: [0]
TRAIN: [0 2] TEST: [3]
See also
--------
Bootstrap: cross-validation using re-sampling with replacement.
"""
def _iter_indices(self):
rng = check_random_state(self.random_state)
for i in range(self.n_iter):
# random partition
permutation = rng.permutation(self.n)
ind_test = permutation[:self.n_test]
ind_train = permutation[self.n_test:self.n_test + self.n_train]
yield ind_train, ind_test
def __repr__(self):
return ('%s(%d, n_iter=%d, test_size=%s, '
'random_state=%s)' % (
self.__class__.__name__,
self.n,
self.n_iter,
str(self.test_size),
self.random_state,
))
def __len__(self):
return self.n_iter
def _validate_shuffle_split(n, test_size, train_size):
if test_size is None and train_size is None:
raise ValueError(
'test_size and train_size can not both be None')
if test_size is not None:
if np.asarray(test_size).dtype.kind == 'f':
if test_size >= 1.:
raise ValueError(
'test_size=%f should be smaller '
'than 1.0 or be an integer' % test_size)
elif np.asarray(test_size).dtype.kind == 'i':
if test_size >= n:
raise ValueError(
'test_size=%d should be smaller '
'than the number of samples %d' % (test_size, n))
else:
raise ValueError("Invalid value for test_size: %r" % test_size)
if train_size is not None:
if np.asarray(train_size).dtype.kind == 'f':
if train_size >= 1.:
raise ValueError("train_size=%f should be smaller "
"than 1.0 or be an integer" % train_size)
elif np.asarray(test_size).dtype.kind == 'f' and \
train_size + test_size > 1.:
raise ValueError('The sum of test_size and train_size = %f, '
'should be smaller than 1.0. Reduce '
'test_size and/or train_size.' %
(train_size + test_size))
elif np.asarray(train_size).dtype.kind == 'i':
if train_size >= n:
raise ValueError("train_size=%d should be smaller "
"than the number of samples %d" %
(train_size, n))
else:
raise ValueError("Invalid value for train_size: %r" % train_size)
if np.asarray(test_size).dtype.kind == 'f':
n_test = ceil(test_size * n)
elif np.asarray(test_size).dtype.kind == 'i':
n_test = float(test_size)
if train_size is None:
n_train = n - n_test
else:
if np.asarray(train_size).dtype.kind == 'f':
n_train = floor(train_size * n)
else:
n_train = float(train_size)
if test_size is None:
n_test = n - n_train
if n_train + n_test > n:
raise ValueError('The sum of train_size and test_size = %d, '
'should be smaller than the number of '
'samples %d. Reduce test_size and/or '
'train_size.' % (n_train + n_test, n))
return int(n_train), int(n_test)
class StratifiedShuffleSplit(BaseShuffleSplit):
"""Stratified ShuffleSplit cross validation iterator
Provides train/test indices to split data in train test sets.
This cross-validation object is a merge of StratifiedKFold and
ShuffleSplit, which returns stratified randomized folds. The folds
are made by preserving the percentage of samples for each class.
Note: like the ShuffleSplit strategy, stratified random splits
do not guarantee that all folds will be different, although this is
still very likely for sizeable datasets.
Parameters
----------
y : array, [n_samples]
Labels of samples.
n_iter : int (default 10)
Number of re-shuffling & splitting iterations.
test_size : float (default 0.1), int, or None
If float, should be between 0.0 and 1.0 and represent the
proportion of the dataset to include in the test split. If
int, represents the absolute number of test samples. If None,
the value is automatically set to the complement of the train size.
train_size : float, int, or None (default is None)
If float, should be between 0.0 and 1.0 and represent the
proportion of the dataset to include in the train split. If
int, represents the absolute number of train samples. If None,
the value is automatically set to the complement of the test size.
random_state : int or RandomState
Pseudo-random number generator state used for random sampling.
Examples
--------
>>> from sklearn.cross_validation import StratifiedShuffleSplit
>>> X = np.array([[1, 2], [3, 4], [1, 2], [3, 4]])
>>> y = np.array([0, 0, 1, 1])
>>> sss = StratifiedShuffleSplit(y, 3, test_size=0.5, random_state=0)
>>> len(sss)
3
>>> print(sss) # doctest: +ELLIPSIS
StratifiedShuffleSplit(labels=[0 0 1 1], n_iter=3, ...)
>>> for train_index, test_index in sss:
... print("TRAIN:", train_index, "TEST:", test_index)
... X_train, X_test = X[train_index], X[test_index]
... y_train, y_test = y[train_index], y[test_index]
TRAIN: [1 2] TEST: [3 0]
TRAIN: [0 2] TEST: [1 3]
TRAIN: [0 2] TEST: [3 1]
"""
def __init__(self, y, n_iter=10, test_size=0.1, train_size=None,
indices=None, random_state=None, n_iterations=None):
super(StratifiedShuffleSplit, self).__init__(
len(y), n_iter, test_size, train_size, indices, random_state,
n_iterations)
self.y = np.array(y)
self.classes, self.y_indices = np.unique(y, return_inverse=True)
n_cls = self.classes.shape[0]
if np.min(np.bincount(self.y_indices)) < 2:
raise ValueError("The least populated class in y has only 1"
" member, which is too few. The minimum"
" number of labels for any class cannot"
" be less than 2.")
if self.n_train < n_cls:
raise ValueError('The train_size = %d should be greater or '
'equal to the number of classes = %d' %
(self.n_train, n_cls))
if self.n_test < n_cls:
raise ValueError('The test_size = %d should be greater or '
'equal to the number of classes = %d' %
(self.n_test, n_cls))
def _iter_indices(self):
rng = check_random_state(self.random_state)
cls_count = np.bincount(self.y_indices)
p_i = cls_count / float(self.n)
n_i = np.round(self.n_train * p_i).astype(int)
t_i = np.minimum(cls_count - n_i,
np.round(self.n_test * p_i).astype(int))
for n in range(self.n_iter):
train = []
test = []
for i, cls in enumerate(self.classes):
permutation = rng.permutation(cls_count[i])
cls_i = np.where((self.y == cls))[0][permutation]
train.extend(cls_i[:n_i[i]])
test.extend(cls_i[n_i[i]:n_i[i] + t_i[i]])
# Because of rounding issues (as n_train and n_test are not
# dividers of the number of elements per class), we may end
# up here with less samples in train and test than asked for.
if len(train) < self.n_train or len(test) < self.n_test:
# We complete by affecting randomly the missing indexes
missing_idx = np.where(np.bincount(train + test,
minlength=len(self.y)) == 0,
)[0]
missing_idx = rng.permutation(missing_idx)
train.extend(missing_idx[:(self.n_train - len(train))])
test.extend(missing_idx[-(self.n_test - len(test)):])
train = rng.permutation(train)
test = rng.permutation(test)
yield train, test
def __repr__(self):
return ('%s(labels=%s, n_iter=%d, test_size=%s, '
'random_state=%s)' % (
self.__class__.__name__,
self.y,
self.n_iter,
str(self.test_size),
self.random_state,
))
def __len__(self):
return self.n_iter
##############################################################################
def cross_val_score(estimator, X, y=None, scoring=None, cv=None, n_jobs=1,
verbose=0, fit_params=None, pre_dispatch='2*n_jobs'):
"""Evaluate a score by cross-validation
Parameters
----------
estimator : estimator object implementing 'fit'
The object to use to fit the data.
X : array-like
The data to fit. Can be, for example a list, or an array at least 2d.
y : array-like, optional, default: None
The target variable to try to predict in the case of
supervised learning.
scoring : string, callable or None, optional, default: None
A string (see model evaluation documentation) or
a scorer callable object / function with signature
``scorer(estimator, X, y)``.
cv : cross-validation generator or int, optional, default: None
A cross-validation generator to use. If int, determines
the number of folds in StratifiedKFold if y is binary
or multiclass and estimator is a classifier, or the number
of folds in KFold otherwise. If None, it is equivalent to cv=3.
n_jobs : integer, optional
The number of CPUs to use to do the computation. -1 means
'all CPUs'.
verbose : integer, optional
The verbosity level.
fit_params : dict, optional
Parameters to pass to the fit method of the estimator.
pre_dispatch : int, or string, optional
Controls the number of jobs that get dispatched during parallel
execution. Reducing this number can be useful to avoid an
explosion of memory consumption when more jobs get dispatched
than CPUs can process. This parameter can be:
- None, in which case all the jobs are immediately
created and spawned. Use this for lightweight and
fast-running jobs, to avoid delays due to on-demand
spawning of the jobs
- An int, giving the exact number of total jobs that are
spawned
- A string, giving an expression as a function of n_jobs,
as in '2*n_jobs'
Returns
-------
scores : array of float, shape=(len(list(cv)),)
Array of scores of the estimator for each run of the cross validation.
"""
X, y = indexable(X, y)
cv = _check_cv(cv, X, y, classifier=is_classifier(estimator))
scorer = check_scoring(estimator, scoring=scoring)
# We clone the estimator to make sure that all the folds are
# independent, and that it is pickle-able.
parallel = Parallel(n_jobs=n_jobs, verbose=verbose,
pre_dispatch=pre_dispatch)
scores = parallel(delayed(_fit_and_score)(clone(estimator), X, y, scorer,
train, test, verbose, None,
fit_params)
for train, test in cv)
return np.array(scores)[:, 0]
def _fit_and_score(estimator, X, y, scorer, train, test, verbose, parameters,
fit_params, return_train_score=False,
return_parameters=False):
"""Fit estimator and compute scores for a given dataset split.
Parameters
----------
estimator : estimator object implementing 'fit'
The object to use to fit the data.
X : array-like of shape at least 2D
The data to fit.
y : array-like, optional, default: None
The target variable to try to predict in the case of
supervised learning.
scoring : callable
A scorer callable object / function with signature
``scorer(estimator, X, y)``.
train : array-like, shape = (n_train_samples,)
Indices of training samples.
test : array-like, shape = (n_test_samples,)
Indices of test samples.
verbose : integer
The verbosity level.
parameters : dict or None
Parameters to be set on the estimator.
fit_params : dict or None
Parameters that will be passed to ``estimator.fit``.
return_train_score : boolean, optional, default: False
Compute and return score on training set.
return_parameters : boolean, optional, default: False
Return parameters that has been used for the estimator.
Returns
-------
train_score : float, optional
Score on training set, returned only if `return_train_score` is `True`.
test_score : float
Score on test set.
n_test_samples : int
Number of test samples.
scoring_time : float
Time spent for fitting and scoring in seconds.
parameters : dict or None, optional
The parameters that have been evaluated.
"""
if verbose > 1:
if parameters is None:
msg = "no parameters to be set"
else:
msg = '%s' % (', '.join('%s=%s' % (k, v)
for k, v in parameters.items()))
print("[CV] %s %s" % (msg, (64 - len(msg)) * '.'))
# Adjust lenght of sample weights
n_samples = _num_samples(X)
fit_params = fit_params if fit_params is not None else {}
fit_params = dict([(k, np.asarray(v)[train]
if hasattr(v, '__len__') and len(v) == n_samples else v)
for k, v in fit_params.items()])
if parameters is not None:
estimator.set_params(**parameters)
start_time = time.time()
X_train, y_train = _safe_split(estimator, X, y, train)
X_test, y_test = _safe_split(estimator, X, y, test, train)
if y_train is None:
estimator.fit(X_train, **fit_params)
else:
estimator.fit(X_train, y_train, **fit_params)
test_score = _score(estimator, X_test, y_test, scorer)
if return_train_score:
train_score = _score(estimator, X_train, y_train, scorer)
scoring_time = time.time() - start_time
if verbose > 2:
msg += ", score=%f" % test_score
if verbose > 1:
end_msg = "%s -%s" % (msg, logger.short_format_time(scoring_time))
print("[CV] %s %s" % ((64 - len(end_msg)) * '.', end_msg))
ret = [train_score] if return_train_score else []
ret.extend([test_score, _num_samples(X_test), scoring_time])
if return_parameters:
ret.append(parameters)
return ret
def _safe_split(estimator, X, y, indices, train_indices=None):
"""Create subset of dataset and properly handle kernels."""
if hasattr(estimator, 'kernel') and callable(estimator.kernel):
# cannot compute the kernel values with custom function
raise ValueError("Cannot use a custom kernel function. "
"Precompute the kernel matrix instead.")
if not hasattr(X, "shape"):
if getattr(estimator, "_pairwise", False):
raise ValueError("Precomputed kernels or affinity matrices have "
"to be passed as arrays or sparse matrices.")
X_subset = [X[idx] for idx in indices]
else:
if getattr(estimator, "_pairwise", False):
# X is a precomputed square kernel matrix
if X.shape[0] != X.shape[1]:
raise ValueError("X should be a square kernel matrix")
if train_indices is None:
X_subset = X[np.ix_(indices, indices)]
else:
X_subset = X[np.ix_(indices, train_indices)]
else:
X_subset = safe_indexing(X, indices)
if y is not None:
y_subset = safe_indexing(y, indices)
else:
y_subset = None
return X_subset, y_subset
def _score(estimator, X_test, y_test, scorer):
"""Compute the score of an estimator on a given test set."""
if y_test is None:
score = scorer(estimator, X_test)
else:
score = scorer(estimator, X_test, y_test)
if not isinstance(score, numbers.Number):
raise ValueError("scoring must return a number, got %s (%s) instead."
% (str(score), type(score)))
return score
def _permutation_test_score(estimator, X, y, cv, scorer):
"""Auxiliary function for permutation_test_score"""
avg_score = []
for train, test in cv:
estimator.fit(X[train], y[train])
avg_score.append(scorer(estimator, X[test], y[test]))
return np.mean(avg_score)
def _shuffle(y, labels, random_state):
"""Return a shuffled copy of y eventually shuffle among same labels."""
if labels is None:
ind = random_state.permutation(len(y))
else:
ind = np.arange(len(labels))
for label in np.unique(labels):
this_mask = (labels == label)
ind[this_mask] = random_state.permutation(ind[this_mask])
return y[ind]
def check_cv(cv, X=None, y=None, classifier=False):
"""Input checker utility for building a CV in a user friendly way.
Parameters
----------
cv : int, a cv generator instance, or None
The input specifying which cv generator to use. It can be an
integer, in which case it is the number of folds in a KFold,
None, in which case 3 fold is used, or another object, that
will then be used as a cv generator.
X : array-like
The data the cross-val object will be applied on.
y : array-like
The target variable for a supervised learning problem.
classifier : boolean optional
Whether the task is a classification task, in which case
stratified KFold will be used.
Returns
-------
checked_cv: a cross-validation generator instance.
The return value is guaranteed to be a cv generator instance, whatever
the input type.
"""
return _check_cv(cv, X=X, y=y, classifier=classifier, warn_mask=True)
def _check_cv(cv, X=None, y=None, classifier=False, warn_mask=False):
# This exists for internal use while indices is being deprecated.
is_sparse = sp.issparse(X)
needs_indices = is_sparse or not hasattr(X, "shape")
if cv is None:
cv = 3
if isinstance(cv, numbers.Integral):
if warn_mask and not needs_indices:
warnings.warn('check_cv will return indices instead of boolean '
'masks from 0.17', DeprecationWarning)
else:
needs_indices = None
if classifier:
if type_of_target(y) in ['binary', 'multiclass']:
cv = StratifiedKFold(y, cv, indices=needs_indices)
else:
cv = KFold(_num_samples(y), cv, indices=needs_indices)
else:
if not is_sparse:
n_samples = len(X)
else:
n_samples = X.shape[0]
cv = KFold(n_samples, cv, indices=needs_indices)
if needs_indices and not getattr(cv, "_indices", True):
raise ValueError("Sparse data and lists require indices-based cross"
" validation generator, got: %r", cv)
return cv
def permutation_test_score(estimator, X, y, cv=None,
n_permutations=100, n_jobs=1, labels=None,
random_state=0, verbose=0, scoring=None):
"""Evaluate the significance of a cross-validated score with permutations
Parameters
----------
estimator : estimator object implementing 'fit'
The object to use to fit the data.
X : array-like of shape at least 2D
The data to fit.
y : array-like
The target variable to try to predict in the case of
supervised learning.
scoring : string, callable or None, optional, default: None
A string (see model evaluation documentation) or
a scorer callable object / function with signature
``scorer(estimator, X, y)``.
cv : integer or cross-validation generator, optional
If an integer is passed, it is the number of fold (default 3).
Specific cross-validation objects can be passed, see
sklearn.cross_validation module for the list of possible objects.
n_permutations : integer, optional
Number of times to permute ``y``.
n_jobs : integer, optional
The number of CPUs to use to do the computation. -1 means
'all CPUs'.
labels : array-like of shape [n_samples] (optional)
Labels constrain the permutation among groups of samples with
a same label.
random_state : RandomState or an int seed (0 by default)
A random number generator instance to define the state of the
random permutations generator.
verbose : integer, optional
The verbosity level.
Returns
-------
score : float
The true score without permuting targets.
permutation_scores : array, shape = [n_permutations]
The scores obtained for each permutations.
pvalue : float
The returned value equals p-value if `scoring` returns bigger
numbers for better scores (e.g., accuracy_score). If `scoring` is
rather a loss function (i.e. when lower is better such as with
`mean_squared_error`) then this is actually the complement of the
p-value: 1 - p-value.
Notes
-----
This function implements Test 1 in:
Ojala and Garriga. Permutation Tests for Studying Classifier
Performance. The Journal of Machine Learning Research (2010)
vol. 11
"""
X, y = indexable(X, y)
cv = _check_cv(cv, X, y, classifier=is_classifier(estimator))
scorer = check_scoring(estimator, scoring=scoring)
random_state = check_random_state(random_state)
# We clone the estimator to make sure that all the folds are
# independent, and that it is pickle-able.
score = _permutation_test_score(clone(estimator), X, y, cv, scorer)
permutation_scores = Parallel(n_jobs=n_jobs, verbose=verbose)(
delayed(_permutation_test_score)(
clone(estimator), X, _shuffle(y, labels, random_state), cv,
scorer)
for _ in range(n_permutations))
permutation_scores = np.array(permutation_scores)
pvalue = (np.sum(permutation_scores >= score) + 1.0) / (n_permutations + 1)
return score, permutation_scores, pvalue
permutation_test_score.__test__ = False # to avoid a pb with nosetests
def train_test_split(*arrays, **options):
"""Split arrays or matrices into random train and test subsets
Quick utility that wraps input validation and
``next(iter(ShuffleSplit(n_samples)))`` and application to input
data into a single call for splitting (and optionally subsampling)
data in a oneliner.
Parameters
----------
*arrays : sequence of arrays or scipy.sparse matrices with same shape[0]
Python lists or tuples occurring in arrays are converted to 1D numpy
arrays.
test_size : float, int, or None (default is None)
If float, should be between 0.0 and 1.0 and represent the
proportion of the dataset to include in the test split. If
int, represents the absolute number of test samples. If None,
the value is automatically set to the complement of the train size.
If train size is also None, test size is set to 0.25.
train_size : float, int, or None (default is None)
If float, should be between 0.0 and 1.0 and represent the
proportion of the dataset to include in the train split. If
int, represents the absolute number of train samples. If None,
the value is automatically set to the complement of the test size.
random_state : int or RandomState
Pseudo-random number generator state used for random sampling.
Returns
-------
splitting : list of arrays, length=2 * len(arrays)
List containing train-test split of input array.
Examples
--------
>>> import numpy as np
>>> from sklearn.cross_validation import train_test_split
>>> a, b = np.arange(10).reshape((5, 2)), range(5)
>>> a
array([[0, 1],
[2, 3],
[4, 5],
[6, 7],
[8, 9]])
>>> list(b)
[0, 1, 2, 3, 4]
>>> a_train, a_test, b_train, b_test = train_test_split(
... a, b, test_size=0.33, random_state=42)
...
>>> a_train
array([[4, 5],
[0, 1],
[6, 7]])
>>> b_train
[2, 0, 3]
>>> a_test
array([[2, 3],
[8, 9]])
>>> b_test
[1, 4]
"""
n_arrays = len(arrays)
if n_arrays == 0:
raise ValueError("At least one array required as input")
test_size = options.pop('test_size', None)
train_size = options.pop('train_size', None)
random_state = options.pop('random_state', None)
dtype = options.pop('dtype', None)
if dtype is not None:
warnings.warn("dtype option is ignored and will be removed in 0.18.")
force_arrays = options.pop('force_arrays', False)
if options:
raise TypeError("Invalid parameters passed: %s" % str(options))
if force_arrays:
warnings.warn("The force_arrays option is deprecated and will be "
"removed in 0.18.", DeprecationWarning)
arrays = [check_array(x, 'csr', ensure_2d=False, force_all_finite=False)
if x is not None else x for x in arrays]
if test_size is None and train_size is None:
test_size = 0.25
arrays = indexable(*arrays)
n_samples = _num_samples(arrays[0])
cv = ShuffleSplit(n_samples, test_size=test_size,
train_size=train_size,
random_state=random_state)
train, test = next(iter(cv))
return list(chain.from_iterable((safe_indexing(a, train),
safe_indexing(a, test)) for a in arrays))
train_test_split.__test__ = False # to avoid a pb with nosetests