make_imbalance

imbens.datasets.make_imbalance(X, y, *, sampling_strategy=None, random_state=None, verbose=False, **kwargs)[source]

Turns a dataset into an imbalanced dataset with a specific sampling strategy.

A simple toy dataset to visualize clustering and classification algorithms.ss

Read more in the User Guide.

Parameters:

X{array-like, dataframe} of shape (n_samples, n_features)

Matrix containing the data to be imbalanced.

yndarray of shape (n_samples,)

Corresponding label for each sample in X.

sampling_strategydict or callable,

Ratio to use for resampling the data set.

When dict, the keys correspond to the targeted classes. The values correspond to the desired number of samples for each targeted class.
When callable, function taking y and returns a dict. The keys correspond to the targeted classes. The values correspond to the desired number of samples for each class.

random_stateint, RandomState instance or None, 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.

verbosebool, default=False

Show information regarding the sampling.

kwargsdict

Dictionary of additional keyword arguments to pass to sampling_strategy.

Returns:

X_resampled{ndarray, dataframe} of shape (n_samples_new, n_features): The array containing the imbalanced data.
y_resampledndarray of shape (n_samples_new): The corresponding label of X_resampled.

Notes

See Make a dataset class-imbalanced for an example.

Examples

>>> from collections import Counter
>>> from sklearn.datasets import load_iris
>>> from imbens.datasets import make_imbalance

>>> data = load_iris()
>>> X, y = data.data, data.target
>>> print(f'Distribution before imbalancing: {Counter(y)}')
Distribution before imbalancing: Counter({0: 50, 1: 50, 2: 50})
>>> X_res, y_res = make_imbalance(X, y,
...                               sampling_strategy={0: 10, 1: 20, 2: 30},
...                               random_state=42)
>>> print(f'Distribution after imbalancing: {Counter(y_res)}')
Distribution after imbalancing: Counter({2: 30, 1: 20, 0: 10})