""" The :mod:`sklearn.cross_validation` module includes utilities for cross- validation and performance evaluation. """ # Author: Alexandre Gramfort , # Gael Varoquaux , # Olivier Grisel # 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 (_is_arraylike, _num_samples, check_array, column_or_1d) 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 from .utils.fixes import bincount __all__ = ['KFold', 'LabelKFold', 'LeaveOneLabelOut', 'LeaveOneOut', 'LeavePLabelOut', 'LeavePOut', 'ShuffleSplit', 'StratifiedKFold', 'StratifiedShuffleSplit', 'PredefinedSplit', 'LabelShuffleSplit', 'check_cv', 'cross_val_score', 'cross_val_predict', '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): if abs(n - int(n)) >= np.finfo('f').eps: raise ValueError("n must be an integer") self.n = int(n) def __iter__(self): ind = np.arange(self.n) for test_index in self._iter_test_masks(): train_index = np.logical_not(test_index) 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. Read more in the :ref:`User Guide `. 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. Read more in the :ref:`User Guide `. 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): super(LeavePOut, self).__init__(n) 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, shuffle, random_state): super(_BaseKFold, self).__init__(n) 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 by default). Each fold is then used a validation set once while the k - 1 remaining fold form the training set. Read more in the :ref:`User Guide `. 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 When shuffle=True, pseudo-random number generator state used for shuffling. If None, use default numpy RNG for shuffling. Examples -------- >>> from sklearn.cross_validation import KFold >>> X = np.array([[1, 2], [3, 4], [1, 2], [3, 4]]) >>> y = np.array([1, 2, 3, 4]) >>> kf = 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). LabelKFold: K-fold iterator variant with non-overlapping labels. """ def __init__(self, n, n_folds=3, shuffle=False, random_state=None): super(KFold, self).__init__(n, n_folds, 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 LabelKFold(_BaseKFold): """K-fold iterator variant with non-overlapping labels. The same label will not appear in two different folds (the number of distinct labels has to be at least equal to the number of folds). The folds are approximately balanced in the sense that the number of distinct labels is approximately the same in each fold. .. versionadded:: 0.17 Parameters ---------- labels : array-like with shape (n_samples, ) Contains a label for each sample. The folds are built so that the same label does not appear in two different folds. n_folds : int, default=3 Number of folds. Must be at least 2. Examples -------- >>> from sklearn.cross_validation import LabelKFold >>> X = np.array([[1, 2], [3, 4], [5, 6], [7, 8]]) >>> y = np.array([1, 2, 3, 4]) >>> labels = np.array([0, 0, 2, 2]) >>> label_kfold = LabelKFold(labels, n_folds=2) >>> len(label_kfold) 2 >>> print(label_kfold) sklearn.cross_validation.LabelKFold(n_labels=4, n_folds=2) >>> for train_index, test_index in label_kfold: ... 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: [0 1] TEST: [2 3] [[1 2] [3 4]] [[5 6] [7 8]] [1 2] [3 4] TRAIN: [2 3] TEST: [0 1] [[5 6] [7 8]] [[1 2] [3 4]] [3 4] [1 2] See also -------- LeaveOneLabelOut for splitting the data according to explicit, domain-specific stratification of the dataset. """ def __init__(self, labels, n_folds=3): super(LabelKFold, self).__init__(len(labels), n_folds, shuffle=False, random_state=None) unique_labels, labels = np.unique(labels, return_inverse=True) n_labels = len(unique_labels) if n_folds > n_labels: raise ValueError( ("Cannot have number of folds n_folds={0} greater" " than the number of labels: {1}.").format(n_folds, n_labels)) # Weight labels by their number of occurences n_samples_per_label = np.bincount(labels) # Distribute the most frequent labels first indices = np.argsort(n_samples_per_label)[::-1] n_samples_per_label = n_samples_per_label[indices] # Total weight of each fold n_samples_per_fold = np.zeros(n_folds) # Mapping from label index to fold index label_to_fold = np.zeros(len(unique_labels)) # Distribute samples by adding the largest weight to the lightest fold for label_index, weight in enumerate(n_samples_per_label): lightest_fold = np.argmin(n_samples_per_fold) n_samples_per_fold[lightest_fold] += weight label_to_fold[indices[label_index]] = lightest_fold self.idxs = label_to_fold[labels] def _iter_test_indices(self): for f in range(self.n_folds): yield np.where(self.idxs == f)[0] def __repr__(self): return '{0}.{1}(n_labels={2}, n_folds={3})'.format( self.__class__.__module__, self.__class__.__name__, self.n, self.n_folds, ) 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. Read more in the :ref:`User Guide `. 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 When shuffle=True, pseudo-random number generator state used for shuffling. If None, use default numpy RNG for shuffling. Examples -------- >>> from sklearn.cross_validation import StratifiedKFold >>> X = np.array([[1, 2], [3, 4], [1, 2], [3, 4]]) >>> y = np.array([0, 0, 1, 1]) >>> skf = 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. See also -------- LabelKFold: K-fold iterator variant with non-overlapping labels. """ def __init__(self, y, n_folds=3, shuffle=False, random_state=None): super(StratifiedKFold, self).__init__( len(y), n_folds, shuffle, random_state) y = np.asarray(y) n_samples = y.shape[0] unique_labels, y_inversed = np.unique(y, return_inverse=True) label_counts = 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. Read more in the :ref:`User Guide `. 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] See also -------- LabelKFold: K-fold iterator variant with non-overlapping labels. """ def __init__(self, labels): super(LeaveOneLabelOut, self).__init__(len(labels)) # 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. Read more in the :ref:`User Guide `. 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] See also -------- LabelKFold: K-fold iterator variant with non-overlapping labels. """ def __init__(self, labels, p): # We make a copy of labels to avoid side-effects during iteration super(LeavePLabelOut, self).__init__(len(labels)) 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 BaseShuffleSplit(with_metaclass(ABCMeta)): """Base class for ShuffleSplit and StratifiedShuffleSplit""" def __init__(self, n, n_iter=10, test_size=0.1, train_size=None, random_state=None): self.n = n self.n_iter = n_iter self.test_size = test_size self.train_size = train_size self.random_state = random_state self.n_train, self.n_test = _validate_shuffle_split(n, test_size, train_size) def __iter__(self): for train, test in self._iter_indices(): yield train, test return @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. Read more in the :ref:`User Guide `. 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] """ 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. Read more in the :ref:`User Guide `. 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, random_state=None): super(StratifiedShuffleSplit, self).__init__( len(y), n_iter, test_size, train_size, random_state) 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(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 = 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(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 class PredefinedSplit(_PartitionIterator): """Predefined split cross validation iterator Splits the data into training/test set folds according to a predefined scheme. Each sample can be assigned to at most one test set fold, as specified by the user through the ``test_fold`` parameter. Read more in the :ref:`User Guide `. Parameters ---------- test_fold : "array-like, shape (n_samples,) test_fold[i] gives the test set fold of sample i. A value of -1 indicates that the corresponding sample is not part of any test set folds, but will instead always be put into the training fold. Examples -------- >>> from sklearn.cross_validation import PredefinedSplit >>> X = np.array([[1, 2], [3, 4], [1, 2], [3, 4]]) >>> y = np.array([0, 0, 1, 1]) >>> ps = PredefinedSplit(test_fold=[0, 1, -1, 1]) >>> len(ps) 2 >>> print(ps) # doctest: +NORMALIZE_WHITESPACE +ELLIPSIS sklearn.cross_validation.PredefinedSplit(test_fold=[ 0 1 -1 1]) >>> for train_index, test_index in ps: ... 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 3] TEST: [0] TRAIN: [0 2] TEST: [1 3] """ def __init__(self, test_fold): super(PredefinedSplit, self).__init__(len(test_fold)) self.test_fold = np.array(test_fold, dtype=np.int) self.test_fold = column_or_1d(self.test_fold) self.unique_folds = np.unique(self.test_fold) self.unique_folds = self.unique_folds[self.unique_folds != -1] def _iter_test_indices(self): for f in self.unique_folds: yield np.where(self.test_fold == f)[0] def __repr__(self): return '%s.%s(test_fold=%s)' % ( self.__class__.__module__, self.__class__.__name__, self.test_fold) def __len__(self): return len(self.unique_folds) class LabelShuffleSplit(ShuffleSplit): """Shuffle-Labels-Out cross-validation iterator Provides randomized 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 LabelShuffleSplit is that the former generates splits using all subsets of size ``p`` unique labels, whereas LabelShuffleSplit generates a user-determined number of random test splits, each with a user-determined fraction of unique labels. For example, a less computationally intensive alternative to ``LeavePLabelOut(labels, p=10)`` would be ``LabelShuffleSplit(labels, test_size=10, n_iter=100)``. Note: The parameters ``test_size`` and ``train_size`` refer to labels, and not to samples, as in ShuffleSplit. .. versionadded:: 0.17 Parameters ---------- labels : array, [n_samples] Labels of samples n_iter : int (default 5) Number of re-shuffling and splitting iterations. test_size : float (default 0.2), int, or None If float, should be between 0.0 and 1.0 and represent the proportion of the labels to include in the test split. If int, represents the absolute number of test labels. 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 labels to include in the train split. If int, represents the absolute number of train labels. 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. """ def __init__(self, labels, n_iter=5, test_size=0.2, train_size=None, random_state=None): classes, label_indices = np.unique(labels, return_inverse=True) super(LabelShuffleSplit, self).__init__( len(classes), n_iter=n_iter, test_size=test_size, train_size=train_size, random_state=random_state) self.labels = labels self.classes = classes self.label_indices = label_indices def __repr__(self): return ('%s(labels=%s, n_iter=%d, test_size=%s, ' 'random_state=%s)' % ( self.__class__.__name__, self.labels, self.n_iter, str(self.test_size), self.random_state, )) def __len__(self): return self.n_iter def _iter_indices(self): for label_train, label_test in super(LabelShuffleSplit, self)._iter_indices(): # these are the indices of classes in the partition # invert them into data indices train = np.flatnonzero(np.in1d(self.label_indices, label_train)) test = np.flatnonzero(np.in1d(self.label_indices, label_test)) yield train, test ############################################################################## def _index_param_value(X, v, indices): """Private helper function for parameter value indexing.""" if not _is_arraylike(v) or _num_samples(v) != _num_samples(X): # pass through: skip indexing return v if sp.issparse(v): v = v.tocsr() return safe_indexing(v, indices) def cross_val_predict(estimator, X, y=None, cv=None, n_jobs=1, verbose=0, fit_params=None, pre_dispatch='2*n_jobs'): """Generate cross-validated estimates for each input data point Read more in the :ref:`User Guide `. Parameters ---------- estimator : estimator object implementing 'fit' and 'predict' 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. cv : int, cross-validation generator or an iterable, optional Determines the cross-validation splitting strategy. Possible inputs for cv are: - None, to use the default 3-fold cross-validation, - integer, to specify the number of folds. - An object to be used as a cross-validation generator. - An iterable yielding train/test splits. For integer/None inputs, if ``y`` is binary or multiclass, :class:`StratifiedKFold` used. If the estimator is a classifier or if ``y`` is neither binary nor multiclass, :class:`KFold` is used. Refer :ref:`User Guide ` for the various cross-validation strategies that can be used here. 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 ------- preds : ndarray This is the result of calling 'predict' """ X, y = indexable(X, y) cv = check_cv(cv, X, y, classifier=is_classifier(estimator)) # 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) preds_blocks = parallel(delayed(_fit_and_predict)(clone(estimator), X, y, train, test, verbose, fit_params) for train, test in cv) preds = [p for p, _ in preds_blocks] locs = np.concatenate([loc for _, loc in preds_blocks]) if not _check_is_partition(locs, _num_samples(X)): raise ValueError('cross_val_predict only works for partitions') inv_locs = np.empty(len(locs), dtype=int) inv_locs[locs] = np.arange(len(locs)) # Check for sparse predictions if sp.issparse(preds[0]): preds = sp.vstack(preds, format=preds[0].format) else: preds = np.concatenate(preds) return preds[inv_locs] def _fit_and_predict(estimator, X, y, train, test, verbose, fit_params): """Fit estimator and predict values for a given dataset split. Read more in the :ref:`User Guide `. Parameters ---------- estimator : estimator object implementing 'fit' and 'predict' 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. 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. fit_params : dict or None Parameters that will be passed to ``estimator.fit``. Returns ------- preds : sequence Result of calling 'estimator.predict' test : array-like This is the value of the test parameter """ # Adjust length of sample weights fit_params = fit_params if fit_params is not None else {} fit_params = dict([(k, _index_param_value(X, v, train)) for k, v in fit_params.items()]) X_train, y_train = _safe_split(estimator, X, y, train) X_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) preds = estimator.predict(X_test) return preds, test def _check_is_partition(locs, n): """Check whether locs is a reordering of the array np.arange(n) Parameters ---------- locs : ndarray integer array to test n : int number of expected elements Returns ------- is_partition : bool True iff sorted(locs) is range(n) """ if len(locs) != n: return False hit = np.zeros(n, bool) hit[locs] = True if not np.all(hit): return False return True 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 Read more in the :ref:`User Guide `. 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 : int, cross-validation generator or an iterable, optional Determines the cross-validation splitting strategy. Possible inputs for cv are: - None, to use the default 3-fold cross-validation, - integer, to specify the number of folds. - An object to be used as a cross-validation generator. - An iterable yielding train/test splits. For integer/None inputs, if ``y`` is binary or multiclass, :class:`StratifiedKFold` used. If the estimator is a classifier or if ``y`` is neither binary nor multiclass, :class:`KFold` is used. Refer :ref:`User Guide ` for the various cross-validation strategies that can be used here. 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] class FitFailedWarning(RuntimeWarning): pass def _fit_and_score(estimator, X, y, scorer, train, test, verbose, parameters, fit_params, return_train_score=False, return_parameters=False, error_score='raise'): """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. scorer : 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. error_score : 'raise' (default) or numeric Value to assign to the score if an error occurs in estimator fitting. If set to 'raise', the error is raised. If a numeric value is given, FitFailedWarning is raised. This parameter does not affect the refit step, which will always raise the error. 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 length of sample weights fit_params = fit_params if fit_params is not None else {} fit_params = dict([(k, _index_param_value(X, v, train)) 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) try: if y_train is None: estimator.fit(X_train, **fit_params) else: estimator.fit(X_train, y_train, **fit_params) except Exception as e: if error_score == 'raise': raise elif isinstance(error_score, numbers.Number): test_score = error_score if return_train_score: train_score = error_score warnings.warn("Classifier fit failed. The score on this train-test" " partition for these parameters will be set to %f. " "Details: \n%r" % (error_score, e), FitFailedWarning) else: raise ValueError("error_score must be the string 'raise' or a" " numeric value. (Hint: if using 'raise', please" " make sure that it has been spelled correctly.)" ) else: 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, cross-validation generator or an iterable, optional Determines the cross-validation splitting strategy. Possible inputs for cv are: - None, to use the default 3-fold cross-validation, - integer, to specify the number of folds. - An object to be used as a cross-validation generator. - An iterable yielding train/test splits. For integer/None inputs, if ``y`` is binary or multiclass, :class:`StratifiedKFold` used. If the estimator is a classifier or if ``y`` is neither binary nor multiclass, :class:`KFold` is used. Refer :ref:`User Guide ` for the various cross-validation strategies that can be used here. 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. """ is_sparse = sp.issparse(X) if cv is None: cv = 3 if isinstance(cv, numbers.Integral): if classifier: if type_of_target(y) in ['binary', 'multiclass']: cv = StratifiedKFold(y, cv) else: cv = KFold(_num_samples(y), cv) else: if not is_sparse: n_samples = len(X) else: n_samples = X.shape[0] cv = KFold(n_samples, 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 Read more in the :ref:`User Guide `. 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 : int, cross-validation generator or an iterable, optional Determines the cross-validation splitting strategy. Possible inputs for cv are: - None, to use the default 3-fold cross-validation, - integer, to specify the number of folds. - An object to be used as a cross-validation generator. - An iterable yielding train/test splits. For integer/None inputs, if ``y`` is binary or multiclass, :class:`StratifiedKFold` used. If the estimator is a classifier or if ``y`` is neither binary nor multiclass, :class:`KFold` is used. Refer :ref:`User Guide ` for the various cross-validation strategies that can be used here. 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. Read more in the :ref:`User Guide `. Parameters ---------- *arrays : sequence of indexables with same length / shape[0] allowed inputs are lists, numpy arrays, scipy-sparse matrices or pandas dataframes. .. versionadded:: 0.16 preserves input type instead of always casting to numpy array. 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. stratify : array-like or None (default is None) If not None, data is split in a stratified fashion, using this as the labels array. .. versionadded:: 0.17 *stratify* splitting Returns ------- splitting : list, length = 2 * len(arrays), List containing train-test split of inputs. .. versionadded:: 0.16 Output type is the same as the input type. Examples -------- >>> import numpy as np >>> from sklearn.cross_validation import train_test_split >>> X, y = np.arange(10).reshape((5, 2)), range(5) >>> X array([[0, 1], [2, 3], [4, 5], [6, 7], [8, 9]]) >>> list(y) [0, 1, 2, 3, 4] >>> X_train, X_test, y_train, y_test = train_test_split( ... X, y, test_size=0.33, random_state=42) ... >>> X_train array([[4, 5], [0, 1], [6, 7]]) >>> y_train [2, 0, 3] >>> X_test array([[2, 3], [8, 9]]) >>> y_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.", DeprecationWarning) allow_nd = options.pop('allow_nd', None) allow_lists = options.pop('allow_lists', None) stratify = options.pop('stratify', None) if allow_lists is not None: warnings.warn("The allow_lists option is deprecated and will be " "assumed True in 0.18 and removed.", DeprecationWarning) if options: raise TypeError("Invalid parameters passed: %s" % str(options)) if allow_nd is not None: warnings.warn("The allow_nd option is deprecated and will be " "assumed True in 0.18 and removed.", DeprecationWarning) if allow_lists is False or allow_nd is False: arrays = [check_array(x, 'csr', allow_nd=allow_nd, force_all_finite=False, ensure_2d=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) if stratify is not None: cv = StratifiedShuffleSplit(stratify, test_size=test_size, train_size=train_size, random_state=random_state) else: 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