Accessors and indexers for the different parts of a fold.
training(x = NULL, fold = NULL) validation(x = NULL, fold = NULL) fold_index(x = NULL, fold = NULL)
an object to be indexed by a training set, validation set, or fold index. If missing, the index itself will be returned.
Fold; the fold used to do the indexing. If missing,
will be pulled from the calling environment, if available.
The elements of
x corresponding to the indexes, or the
indexes themselves if
x is missing.