# Author: Hamzeh Alsalhi # # License: BSD 3 clause from __future__ import division import numpy as np import scipy.sparse as sp import array from sklearn.utils import check_random_state from ._random import sample_without_replacement from .deprecation import deprecated __all__ = ['sample_without_replacement', 'choice'] # This is a backport of np.random.choice from numpy 1.7 # The function can be removed when we bump the requirements to >=1.7 @deprecated("sklearn.utils.random.choice was deprecated in version 0.19 " "and will be removed in 0.21. Use np.random.choice or " "np.random.RandomState.choice instead.") def choice(a, size=None, replace=True, p=None, random_state=None): """ choice(a, size=None, replace=True, p=None) Generates a random sample from a given 1-D array .. versionadded:: 1.7.0 Parameters ----------- a : 1-D array-like or int If an ndarray, a random sample is generated from its elements. If an int, the random sample is generated as if a was np.arange(n) size : int or tuple of ints, optional Output shape. Default is None, in which case a single value is returned. replace : boolean, optional Whether the sample is with or without replacement. p : 1-D array-like, optional The probabilities associated with each entry in a. If not given the sample assumes a uniform distribution over all entries in a. random_state : int, RandomState instance or None, optional (default=None) If int, random_state is the seed used by the random number generator; If RandomState instance, random_state is the random number generator; If None, the random number generator is the RandomState instance used by `np.random`. Returns -------- samples : 1-D ndarray, shape (size,) The generated random samples Raises ------- ValueError If a is an int and less than zero, if a or p are not 1-dimensional, if a is an array-like of size 0, if p is not a vector of probabilities, if a and p have different lengths, or if replace=False and the sample size is greater than the population size See Also --------- randint, shuffle, permutation Examples --------- Generate a uniform random sample from np.arange(5) of size 3: >>> np.random.choice(5, 3) # doctest: +SKIP array([0, 3, 4]) >>> #This is equivalent to np.random.randint(0,5,3) Generate a non-uniform random sample from np.arange(5) of size 3: >>> np.random.choice(5, 3, p=[0.1, 0, 0.3, 0.6, 0]) # doctest: +SKIP array([3, 3, 0]) Generate a uniform random sample from np.arange(5) of size 3 without replacement: >>> np.random.choice(5, 3, replace=False) # doctest: +SKIP array([3,1,0]) >>> #This is equivalent to np.random.shuffle(np.arange(5))[:3] Generate a non-uniform random sample from np.arange(5) of size 3 without replacement: >>> np.random.choice(5, 3, replace=False, p=[0.1, 0, 0.3, 0.6, 0]) ... # doctest: +SKIP array([2, 3, 0]) Any of the above can be repeated with an arbitrary array-like instead of just integers. For instance: >>> aa_milne_arr = ['pooh', 'rabbit', 'piglet', 'Christopher'] >>> np.random.choice(aa_milne_arr, 5, p=[0.5, 0.1, 0.1, 0.3]) ... # doctest: +SKIP array(['pooh', 'pooh', 'pooh', 'Christopher', 'piglet'], dtype='|S11') """ if random_state is not None: random_state = check_random_state(random_state) return random_state.choice(a, size, replace, p) else: return np.random.choice(a, size, replace, p) def random_choice_csc(n_samples, classes, class_probability=None, random_state=None): """Generate a sparse random matrix given column class distributions Parameters ---------- n_samples : int, Number of samples to draw in each column. classes : list of size n_outputs of arrays of size (n_classes,) List of classes for each column. class_probability : list of size n_outputs of arrays of size (n_classes,) Optional (default=None). Class distribution of each column. If None the uniform distribution is assumed. random_state : int, RandomState instance or None, optional (default=None) If int, random_state is the seed used by the random number generator; If RandomState instance, random_state is the random number generator; If None, the random number generator is the RandomState instance used by `np.random`. Returns ------- random_matrix : sparse csc matrix of size (n_samples, n_outputs) """ data = array.array('i') indices = array.array('i') indptr = array.array('i', [0]) for j in range(len(classes)): classes[j] = np.asarray(classes[j]) if classes[j].dtype.kind != 'i': raise ValueError("class dtype %s is not supported" % classes[j].dtype) classes[j] = classes[j].astype(np.int64, copy=False) # use uniform distribution if no class_probability is given if class_probability is None: class_prob_j = np.empty(shape=classes[j].shape[0]) class_prob_j.fill(1 / classes[j].shape[0]) else: class_prob_j = np.asarray(class_probability[j]) if not np.isclose(np.sum(class_prob_j), 1.0): raise ValueError("Probability array at index {0} does not sum to " "one".format(j)) if class_prob_j.shape[0] != classes[j].shape[0]: raise ValueError("classes[{0}] (length {1}) and " "class_probability[{0}] (length {2}) have " "different length.".format(j, classes[j].shape[0], class_prob_j.shape[0])) # If 0 is not present in the classes insert it with a probability 0.0 if 0 not in classes[j]: classes[j] = np.insert(classes[j], 0, 0) class_prob_j = np.insert(class_prob_j, 0, 0.0) # If there are nonzero classes choose randomly using class_probability rng = check_random_state(random_state) if classes[j].shape[0] > 1: p_nonzero = 1 - class_prob_j[classes[j] == 0] nnz = int(n_samples * p_nonzero) ind_sample = sample_without_replacement(n_population=n_samples, n_samples=nnz, random_state=random_state) indices.extend(ind_sample) # Normalize probabilities for the nonzero elements classes_j_nonzero = classes[j] != 0 class_probability_nz = class_prob_j[classes_j_nonzero] class_probability_nz_norm = (class_probability_nz / np.sum(class_probability_nz)) classes_ind = np.searchsorted(class_probability_nz_norm.cumsum(), rng.rand(nnz)) data.extend(classes[j][classes_j_nonzero][classes_ind]) indptr.append(len(indices)) return sp.csc_matrix((data, indices, indptr), (n_samples, len(classes)), dtype=int)