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Recursive feature elimination.
A FeaturewiseDatasetMeasure is used to compute sensitivity maps given a certain dataset. These sensitivity maps are in turn used to discard unimportant features. For each feature selection the transfer error on some testdatset is computed. This procedure is repeated until a given StoppingCriterion is reached.
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__sensitivity_analyzer Sensitivity analyzer used to call at each step. |
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__transfer_error Compute transfer error for each feature set. |
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__feature_selector Functor which takes care about removing some features. |
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__train_clf Flag whether training classifier is required. |
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__update_sensitivity Flag whether sensitivity map is recomputed for each step. |
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nfeatures Number of features at each step. Since it is not used by the algorithm it is stored directly in the state variable |
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history Store the last step # when the feature was still present |
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Initialize recursive feature elimination :Parameters: sensitivity_analyzer : FeaturewiseDatasetMeasure object transfer_error : TransferError object used to compute the transfer error of a classifier based on a certain feature set on the test dataset. NOTE: If sensitivity analyzer is based on the same classifier as transfer_error is using, make sure you initialize transfer_error with train=False, otherwise it would train classifier twice without any necessity. feature_selector : Functor Given a sensitivity map it has to return the ids of those features that should be kept. bestdetector : Functor Given a list of error values it has to return a boolean that signals whether the latest error value is the total minimum. stopping_criterion : Functor Given a list of error values it has to return whether the criterion is fulfilled. train_clf : bool Flag whether the classifier in `transfer_error` should be trained before computing the error. In general this is required, but if the `sensitivity_analyzer` and `transfer_error` share and make use of the same classifier it can be switched off to save CPU cycles. Default `None` checks if sensitivity_analyzer is based on a classifier and doesn't train if so. update_sensitivity : bool If False the sensitivity map is only computed once and reused for each iteration. Otherwise the senstitivities are recomputed at each selection step.
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Proceed and select the features recursively eliminating less important ones. Returns a tuple of two new datasets with the feature subset of
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