AllKNN¶

class
imblearn.under_sampling.
AllKNN
(*, sampling_strategy='auto', n_neighbors=3, kind_sel='all', allow_minority=False, n_jobs=None)[source]¶ Undersample based on the AllKNN method.
This method will apply ENN several time and will vary the number of nearest neighbours.
Read more in the User Guide.
 Parameters
 sampling_strategystr, list or callable
Sampling information to sample the data set.
When
str
, specify the class targeted by the resampling. Note the the number of samples will not be equal in each. Possible choices are:'majority'
: resample only the majority class;'not minority'
: resample all classes but the minority class;'not majority'
: resample all classes but the majority class;'all'
: resample all classes;'auto'
: equivalent to'not minority'
.When
list
, the list contains the classes targeted by the resampling.When callable, function taking
y
and returns adict
. The keys correspond to the targeted classes. The values correspond to the desired number of samples for each class.
 n_neighborsint or estimator object, default=3
If
int
, size of the neighbourhood to consider to compute the nearest neighbors. If object, an estimator that inherits fromKNeighborsMixin
that will be used to find the nearestneighbors. By default, it will be a 3NN. kind_sel{‘all’, ‘mode’}, default=’all’
Strategy to use in order to exclude samples.
If
'all'
, all neighbours will have to agree with the samples of interest to not be excluded.If
'mode'
, the majority vote of the neighbours will be used in order to exclude a sample.
The strategy
"all"
will be less conservative than'mode'
. Thus, more samples will be removed whenkind_sel="all"
generally. allow_minoritybool, default=False
If
True
, it allows the majority classes to become the minority class without early stopping.New in version 0.3.
 n_jobsint, default=None
Number of CPU cores used during the crossvalidation loop.
None
means 1 unless in ajoblib.parallel_backend
context.1
means using all processors. See Glossary for more details.
 Attributes
 sample_indices_ndarray of shape (n_new_samples,)
Indices of the samples selected.
New in version 0.4.
See also
CondensedNearestNeighbour
Undersampling by condensing samples.
EditedNearestNeighbours
Undersampling by editing samples.
RepeatedEditedNearestNeighbours
Undersampling by repeating ENN.
Notes
The method is based on [1].
Supports multiclass resampling. A onevs.rest scheme is used when sampling a class as proposed in [1].
References
 1(1,2)
I. Tomek, “An Experiment with the Edited NearestNeighbor Rule,” IEEE Transactions on Systems, Man, and Cybernetics, vol. 6(6), pp. 448452, June 1976.
Examples
>>> from collections import Counter >>> from sklearn.datasets import make_classification >>> from imblearn.under_sampling import AllKNN >>> 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 %s' % Counter(y)) Original dataset shape Counter({1: 900, 0: 100}) >>> allknn = AllKNN() >>> X_res, y_res = allknn.fit_resample(X, y) >>> print('Resampled dataset shape %s' % Counter(y_res)) Resampled dataset shape Counter({1: 887, 0: 100})
Methods
fit
(X, y)Check inputs and statistics of the sampler.
fit_resample
(X, y)Resample the dataset.
get_params
([deep])Get parameters for this estimator.
set_params
(**params)Set the parameters of this estimator.

fit
(X, y)[source]¶ Check inputs and statistics of the sampler.
You should use
fit_resample
in all cases. Parameters
 X{arraylike, dataframe, sparse matrix} of shape (n_samples, n_features)
Data array.
 yarraylike of shape (n_samples,)
Target array.
 Returns
 selfobject
Return the instance itself.

fit_resample
(X, y)[source]¶ Resample the dataset.
 Parameters
 X{arraylike, dataframe, sparse matrix} of shape (n_samples, n_features)
Matrix containing the data which have to be sampled.
 yarraylike of shape (n_samples,)
Corresponding label for each sample in X.
 Returns
 X_resampled{arraylike, dataframe, sparse matrix} of shape (n_samples_new, n_features)
The array containing the resampled data.
 y_resampledarraylike of shape (n_samples_new,)
The corresponding label of
X_resampled
.

get_params
(deep=True)[source]¶ Get parameters for this estimator.
 Parameters
 deepbool, default=True
If True, will return the parameters for this estimator and contained subobjects that are estimators.
 Returns
 paramsdict
Parameter names mapped to their values.

set_params
(**params)[source]¶ Set the parameters of this estimator.
The method works on simple estimators as well as on nested objects (such as
Pipeline
). The latter have parameters of the form<component>__<parameter>
so that it’s possible to update each component of a nested object. Parameters
 **paramsdict
Estimator parameters.
 Returns
 selfestimator instance
Estimator instance.