Expand an in-memory cohort data.frame into the sequential target-trial layout and return the result as a data.frame — the frame-in/frame-out analogue of expand_parquet(), with no intermediate Parquet.

The cohort arrives as an R data.frame (a list of equal-length columns); columns are marshalled dtype-exactly into a Polars frame (R integer -> Int32, double -> Float64, bit64::integer64 -> Int64), expanded by the verified core, and the six structural columns are marshalled back to an R data.frame. A 64-bit integer column (an integer64, e.g. a large id) round-trips exactly via a pure-safe bit reinterpret (no precision loss).

Usage

expand_df(
  cohort,
  id_col,
  period_col,
  treatment_col,
  eligible_col,
  outcome_col,
  first_period,
  last_period,
  estimand
)

Arguments

cohort

An R data.frame of long person-time rows.

id_col, period_col, treatment_col

Column names in cohort.

eligible_col, outcome_col

Eligibility / outcome column names.

first_period, last_period

Inclusive integer bounds on trial_period.

estimand

"ITT" or "PP". Case-insensitive.

Value

A data.frame with the six structural columns (an integer64 input column is returned as integer64). Errors in the core engine surface as R errors.