This method and function help find which data belong in the analysis and assessment sets.

## Usage

```
complement(x, ...)
# S3 method for rsplit
complement(x, ...)
# S3 method for rof_split
complement(x, ...)
# S3 method for sliding_window_split
complement(x, ...)
# S3 method for sliding_index_split
complement(x, ...)
# S3 method for sliding_period_split
complement(x, ...)
# S3 method for apparent_split
complement(x, ...)
```

## Details

Given an `rsplit`

object, `complement()`

will determine which
of the data rows are contained in the assessment set. To save space,
many of the `rsplit`

objects will not contain indices for the
assessment split.