detail_level |
(optional) Sets the level at which results are computed
and aggregated.
-
ensemble : Results are computed at the ensemble level, i.e. over all
models in the ensemble. This means that, for example, bias-corrected
estimates of model performance are assessed by creating (at least) 20
bootstraps and computing the model performance of the ensemble model for
each bootstrap.
-
hybrid (default): Results are computed at the level of models in an
ensemble. This means that, for example, bias-corrected estimates of model
performance are directly computed using the models in the ensemble. If there
are at least 20 trained models in the ensemble, performance is computed for
each model, in contrast to ensemble where performance is computed for the
ensemble of models. If there are less than 20 trained models in the
ensemble, bootstraps are created so that at least 20 point estimates can be
made.
-
model : Results are computed at the model level. This means that, for
example, bias-corrected estimates of model performance are assessed by
creating (at least) 20 bootstraps and computing the performance of the model
for each bootstrap.
Note that each level of detail has a different interpretation for bootstrap
confidence intervals. For ensemble and model these are the confidence
intervals for the ensemble and an individual model, respectively. That is,
the confidence interval describes the range where an estimate produced by a
respective ensemble or model trained on a repeat of the experiment may be
found with the probability of the confidence level. For hybrid , it
represents the range where any single model trained on a repeat of the
experiment may be found with the probability of the confidence level. By
definition, confidence intervals obtained using hybrid are at least as
wide as those for ensemble . hybrid offers the correct interpretation if
the goal of the analysis is to assess the result of a single, unspecified,
model.
hybrid is generally computationally less expensive then ensemble , which
in turn is somewhat less expensive than model .
A non-default detail_level parameter can be specified for separate
evaluation steps by providing a parameter value in a named list with data
elements, e.g. list("auc_data"="ensemble", "model_performance"="hybrid") .
This parameter can be set for the following data elements: auc_data ,
decision_curve_analyis , model_performance , permutation_vimp ,
ice_data , prediction_data and confusion_matrix .
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