Reads all cleaned RDS files from period_1, period_2, and period_3 directories and combines them into a single data frame.
Arguments
- input_dir
Directory containing period subdirectories (period_1, period_2, period_3). Required (no default) so the function never reads from a package or home directory implicitly.
- output_file
Path where combined RDS file should be saved. Required (no default) so the function never writes to a package or home directory implicitly.