This takes a dataset and a split ID and generates two subsets of the data corresponding to a training set and a holdout.
split_data(data, split_id)dataframe
integer representing the split to construct
Returns an R6 object HTEFold with three public fields:
train - The split to be used for training the plugin estimates
holdout - The split not used for training
in_holdout - A logical vector indicating for each unit whether they lie in the holdout.