Extract Cohorts at Every Stage

Returns a named list of datasets at each step of the enrollment flow, enabling cross-cohort comparisons. Results are reported as a named list, organized by step label. Data mode only.

Usage

cohorts(.flow)

Arguments

.flow

A selecta object created in data mode (data supplied to enroll()).

Value

A named list of cohort snapshots, keyed by step label. Each snapshot is itself a list with:

included

A data.table of participants still in the flow after this step.

excluded

A data.table of participants removed at this step (for exclusion steps; NULL otherwise).

n_included

Integer count of included participants.

n_excluded

Integer count of excluded participants (or NA).

Details

cohorts() replays a data mode flow and captures the dataset at every step, returning a named list keyed by step label (with "_start" for the initial cohort). Each snapshot exposes both the included and the excluded rows together with their counts, which is useful for validating a diagram against the data, auditing why particular participants were dropped, or extracting an intermediate population. After a stratify() or allocate() split, the included and excluded elements of a per-arm step are themselves named lists with one entry per arm; after a factorial (two-level) split the entries are the cells, keyed "<parent>: <child>". A manual-mode flow has no underlying data and therefore raises an error. To obtain only the final analyzed population, use cohort().

See also

cohort for extracting only the final cohort

Other cohort extraction functions: cohort()

Examples

flow <- enroll(selectaex2, id = "patient_id") |>
  exclude("Ineligible", criterion = eligible == FALSE) |>
  endpoint("Final")

stages <- cohorts(flow)
names(stages)
#> [1] "_start"     "Ineligible" "Final"     
stages[["Ineligible"]]$n_excluded
#> [1] 851