DES class

class deslib.des.base.DES(pool_classifiers, k=7, DFP=False, with_IH=False, safe_k=None, IH_rate=0.3, mode='selection')

Base class for a Dynamic Ensemble Selection (DES).

All dynamic ensemble selection techniques should inherit from this class.

Warning: This class should not be instantiated directly, use derived classes instead.

Parameters:

pool_classifiers : list of classifiers

The generated_pool of classifiers trained for the corresponding classification problem. The classifiers should support methods “predict” and “predict_proba”.

k : int (Default = 7)

Number of neighbors used to estimate the competence of the base classifiers.

DFP : Boolean (Default = False)

Determines if the dynamic frienemy pruning is applied.

with_IH : Boolean (Default = False)

Whether the hardness level of the region of competence is used to decide between using the DS algorithm or the KNN for classification of a given query sample.

safe_k : int (default = None)

The size of the indecision region.

IH_rate : float (default = 0.3)

Hardness threshold. If the hardness level of the competence region is lower than the IH_rate the KNN classifier is used. Otherwise, the DS algorithm is used for classification.

mode : String (Default = “selection”)

Whether the technique will perform dynamic selection, dynamic weighting or an hybrid approach for classification.

References

Britto, Alceu S., Robert Sabourin, and Luiz ES Oliveira. “Dynamic selection of classifiers—a comprehensive review.” Pattern Recognition 47.11 (2014): 3665-3680.

R. M. O. Cruz, R. Sabourin, and G. D. Cavalcanti, “Dynamic classifier selection: Recent advances and perspectives,” Information Fusion, vol. 41, pp. 195 – 216, 2018.

classify_instance(query)

Predicts the label of the corresponding query sample.

If self.mode == “selection”, the selected ensemble is combined using the majority voting rule

If self.mode == “weighting”, all base classifiers are used for classification, however their influence in the final decision are weighted according to their estimated competence level. The weighted majority voting scheme is used to combine the decisions of the base classifiers.

If self.mode == “hybrid”, A hybrid Dynamic selection and weighting approach is used. First an ensemble with the competent base classifiers are selected. Then, their decisions are aggregated using the weighted majority voting rule according to its competence level estimates.

Parameters:

query : array of shape = [n_features]

The test sample

Returns:

predicted_label: The predicted label of the query

estimate_competence(query)

Estimate the competence of each base classifier ci the classification of the query sample x. Returns an array containing the level of competence estimated for each base classifier. The size of the vector is equals to the size of the generated_pool of classifiers.

Parameters:

query : array containing the test sample = [n_features]

Returns:

competences : array of shape = [n_classifiers]

The competence level estimated for each base classifier

predict_proba_instance(query)

Predicts the posterior probabilities of the corresponding query sample.

If self.mode == “selection”, the selected ensemble is used to estimate the probabilities. The average rule is used to give probabilities estimates.

If self.mode == “weighting”, all base classifiers are used for estimating the probabilities, however their influence in the final decision are weighted according to their estimated competence level. A weighted average method is used to give the probabilities estimates.

If self.mode == “Hybrid”, A hybrid Dynamic selection and weighting approach is used. First an ensemble with the competent base classifiers are selected. Then, their decisions are aggregated using a weighted average rule to give the probabilities estimates.

Parameters:

query : array of shape = [n_features]

The test sample

Returns

——-

predicted_proba : array = [n_classes] with the probability estimates for all classes

select(competences)

Select the most competent classifier for the classification of the query sample x. The most competent classifier (dcs) or an ensemble with the most competent classifiers (des) is returned

Parameters:

competences : array of shape = [n_classifiers]

The estimated competence level for the base classifiers

Returns:

indices : List of index of the selected base classifier(s)