Merges the CDP into the panel by time period (units before the first differenced period receive NA), then cumulates within each unit to recover the level-form process \(\sum_{s \le t} \hat\mu_s\).
.amg_attach_cdp_level(panel, cdp_df)The panel augmented with a cdp_level column.
A panel data.frame.
Two-column data.frame from
.amg_common_dynamic_process().