imblearn.ensemble.BalanceCascade¶
-
class
imblearn.ensemble.
BalanceCascade
(ratio='auto', return_indices=False, random_state=None, n_max_subset=None, classifier=None, estimator=None, **kwargs)[source][source]¶ Create an ensemble of balanced sets by iteratively under-sampling the imbalanced dataset using an estimator.
This method iteratively select subset and make an ensemble of the different sets. The selection is performed using a specific classifier.
Parameters: ratio : str, dict, or callable, optional (default=’auto’)
Ratio to use for resampling the data set.
- If
str
, has to be one of: (i)'minority'
: resample the minority class; (ii)'majority'
: resample the majority class, (iii)'not minority'
: resample all classes apart of the minority class, (iv)'all'
: resample all classes, and (v)'auto'
: correspond to'all'
with for over-sampling methods and'not minority'
for under-sampling methods. The classes targeted will be over-sampled or under-sampled to achieve an equal number of sample with the majority or minority class. - If
dict
, the keys correspond to the targeted classes. The values correspond to the desired number of samples. - If callable, function taking
y
and returns adict
. The keys correspond to the targeted classes. The values correspond to the desired number of samples.
return_indices : bool, optional (default=True)
Whether or not to return the indices of the samples randomly selected from the majority class.
random_state : int, RandomState instance or None, optional (default=None)
If int,
random_state
is the seed used by the random number generator; IfRandomState
instance, random_state is the random number generator; IfNone
, the random number generator is theRandomState
instance used bynp.random
.n_max_subset : int or None, optional (default=None)
Maximum number of subsets to generate. By default, all data from the training will be selected that could lead to a large number of subsets. We can probably deduce this number empirically.
classifier : str, optional (default=None)
The classifier that will be selected to confront the prediction with the real labels. The choices are the following:
'knn'
,'decision-tree'
,'random-forest'
,'adaboost'
,'gradient-boosting'
, and'linear-svm'
.Deprecated since version 0.2:
classifier
is deprecated from 0.2 and will be replaced in 0.4. Useestimator
instead.estimator : object, optional (default=KNeighborsClassifier())
An estimator inherited from
sklearn.base.ClassifierMixin
and having an attributepredict_proba
.bootstrap : bool, optional (default=True)
Whether to bootstrap the data before each iteration.
**kwargs : keywords
The parameters associated with the classifier provided.
Deprecated since version 0.2:
**kwargs
has been deprecated from 0.2 and will be replaced in 0.4. Useestimator
object instead to pass parameters associated to an estimator.Notes
The method is described in [R25].
Supports mutli-class resampling.
References
[R25] (1, 2) X. Y. Liu, J. Wu and Z. H. Zhou, “Exploratory Undersampling for Class-Imbalance Learning,” in IEEE Transactions on Systems, Man, and Cybernetics, Part B (Cybernetics), vol. 39, no. 2, pp. 539-550, April 2009. Examples
>>> from collections import Counter >>> from sklearn.datasets import make_classification >>> from imblearn.ensemble import BalanceCascade >>> X, y = make_classification(n_classes=2, class_sep=2, ... weights=[0.1, 0.9], n_informative=3, n_redundant=1, flip_y=0, ... n_features=20, n_clusters_per_class=1, n_samples=1000, random_state=10) >>> print('Original dataset shape {}'.format(Counter(y))) Original dataset shape Counter({1: 900, 0: 100}) >>> bc = BalanceCascade(random_state=42) >>> X_res, y_res = bc.fit_sample(X, y) >>> print('Resampled dataset shape {}'.format(Counter(y_res[0]))) Resampled dataset shape Counter({...})
Methods
fit
(X, y)Find the classes statistics before to perform sampling. fit_sample
(X, y)Fit the statistics and resample the data directly. get_params
([deep])Get parameters for this estimator. sample
(X, y)Resample the dataset. set_params
(**params)Set the parameters of this estimator. -
__init__
(ratio='auto', return_indices=False, random_state=None, n_max_subset=None, classifier=None, estimator=None, **kwargs)[source][source]¶
Methods
__init__
([ratio, return_indices, ...])fit
(X, y)Find the classes statistics before to perform sampling. fit_sample
(X, y)Fit the statistics and resample the data directly. get_params
([deep])Get parameters for this estimator. sample
(X, y)Resample the dataset. set_params
(**params)Set the parameters of this estimator. -
fit
(X, y)[source][source]¶ Find the classes statistics before to perform sampling.
Parameters: X : ndarray, shape (n_samples, n_features)
Matrix containing the data which have to be sampled.
y : ndarray, shape (n_samples, )
Corresponding label for each sample in X.
Returns: self : object,
Return self.
-
fit_sample
(X, y)[source]¶ Fit the statistics and resample the data directly.
Parameters: X : ndarray, shape (n_samples, n_features)
Matrix containing the data which have to be sampled.
y : ndarray, shape (n_samples, )
Corresponding label for each sample in X.
Returns: X_resampled : ndarray, shape (n_samples_new, n_features)
The array containing the resampled data.
y_resampled : ndarray, shape (n_samples_new)
The corresponding label of X_resampled
-
get_params
(deep=True)[source]¶ Get parameters for this estimator.
Parameters: deep : boolean, optional
If True, will return the parameters for this estimator and contained subobjects that are estimators.
Returns: params : mapping of string to any
Parameter names mapped to their values.
-
sample
(X, y)[source]¶ Resample the dataset.
Parameters: X : ndarray, shape (n_samples, n_features)
Matrix containing the data which have to be sampled.
y : ndarray, shape (n_samples, )
Corresponding label for each sample in X.
Returns: X_resampled : ndarray, shape (n_samples_new, n_features)
The array containing the resampled data.
y_resampled : ndarray, shape (n_samples_new)
The corresponding label of X_resampled
- If