create_skeleton() strips the feature data from a create_lagged_df() object
but keeps the outcome column(s), any grouping columns, and meta-data which allows the resulting
lagged_df to be used downstream in the forecastML pipeline. The main benefit is
that the custom modeling function passed in train_model() can read data directly from the
disk or a database when the dataset is too large to fit into memory.
create_skeleton(lagged_df)An object of class 'lagged_df' from create_lagged_df(..., type = 'train').
An S3 object of class 'lagged_df' or 'grouped_lagged_df': A list of data.frames with the
outcome column(s) and any grouping columns but with all other features removed.
A special attribute skeleton = TRUE is added.
The output of create_skeleton can be passed into