skactiveml.pool.ContrastiveAL#

class skactiveml.pool.ContrastiveAL(nearest_neighbors_dict=None, clf_embedding_flag_name=None, eps=1e-07, missing_label=nan, random_state=None)[source]#

Bases: SingleAnnotatorPoolQueryStrategy

Contrastive Active Learning (ContrastiveAL)

This class implements the Contrastive Active Learning (ContrastiveAL) query strategy [1], which selects samples similar in the (classifier’s learned) feature space, while the classifier predicts maximally different class-membership probabilities.

Parameters
nearest_neighbors_dictdict, default=None

The parameters passed to the nearest neighboring algorithm sklearn.neighbors.NearestNeighbors.

clf_embedding_flag_namestr or None, default=None

Name of the flag, which is passed to the predict_proba method for getting the (learned) sample representations.

  • If clf_embedding_flag_name=None and predict_proba returns only one output, the input samples X are used.

  • If predict_proba returns two outputs or clf_embedding_name is not None, (proba, embeddings) are expected as outputs.

epsfloat > 0, default=1e-7

Minimum probability threshold to compute log-probabilities.

missing_labelscalar or string or np.nan or None, default=np.nan

Value to represent a missing label.

random_stateNone or int or np.random.RandomState, default=None

The random state to use.

References

1

K. Margatina, G. Vernikos, L. Barrault, and N. Aletras. Active Learning by Acquiring Contrastive Examples. In Conf. Empir. Methods Nat. Lang. Process., pages 650–663, 2021.

Methods

get_metadata_routing()

Get metadata routing of this object.

get_params([deep])

Get parameters for this estimator.

query(X, y, clf[, fit_clf, sample_weight, ...])

Determines for which candidate samples labels are to be queried.

set_params(**params)

Set the parameters of this estimator.
get_metadata_routing()#

Get metadata routing of this object.

Please check User Guide on how the routing mechanism works.

Returns
routingMetadataRequest

A MetadataRequest encapsulating routing information.

get_params(deep=True)#

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.

query(X, y, clf, fit_clf=True, sample_weight=None, candidates=None, batch_size=1, return_utilities=False)[source]#

Determines for which candidate samples labels are to be queried.

Parameters
Xarray-like of shape (n_samples, n_features)

Training data set, usually complete, i.e., including the labeled and unlabeled samples.

yarray-like of shape (n_samples,)

Labels of the training data set (possibly including unlabeled ones indicated by self.missing_label).

clfskactiveml.base.SkactivemlClassifier

Classifier implementing the methods fit and predict_proba.

fit_clfbool, default=True

Defines whether the classifier clf should be fitted on X, y, and sample_weight.

sample_weight: array-like of shape (n_samples), default=None

Weights of training samples in X.

candidatesNone or array-like of shape (n_candidates), dtype=int or array-like of shape (n_candidates, n_features), default=None

  • If candidates is None, the unlabeled samples from (X,y) are considered as candidates.

  • If candidates is of shape (n_candidates,) and of type int, candidates is considered as the indices of the samples in (X,y).

  • If candidates is of shape (n_candidates, *), the candidate samples are directly given in candidates (not necessarily contained in X). This is not supported by all query strategies.

batch_sizeint, default=1

The number of samples to be selected in one AL cycle.

return_utilitiesbool, default=False

If True, also return the utilities based on the query strategy.

Returns
query_indicesnumpy.ndarray of shape (batch_size,)

The query indices indicate for which candidate sample a label is to be queried, e.g., query_indices[0] indicates the first selected sample.

  • If candidates is None or of shape (n_candidates,), the indexing refers to the samples in X.

  • If candidates is of shape (n_candidates, n_features), the indexing refers to the samples in candidates.

utilitiesnumpy.ndarray of shape (batch_size, n_samples) or numpy.ndarray of shape (batch_size, n_candidates)

The utilities of samples after each selected sample of the batch, e.g., utilities[0] indicates the utilities used for selecting the first sample (with index query_indices[0]) of the batch. Utilities for labeled samples will be set to np.nan.

  • If candidates is None or of shape (n_candidates,), the indexing refers to the samples in X.

  • If candidates is of shape (n_candidates, n_features), the indexing refers to the samples in candidates.

set_params(**params)#

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.

Examples using skactiveml.pool.ContrastiveAL#

Contrastive Active Learning (CAL)

Contrastive Active Learning (CAL)