Assign a stepped-wedge treatment schedule — assign_stepped

Splits the clusters into equally sized waves and switches each wave on at start + (wave - 1) * wave_length, the wave's treatment-start period. A row is treated from treatment_start + lag onwards, and the lag periods from treatment_start up to that point are flagged as transition periods instead. The period values are compared as they stand, so they must be on the same scale as start. Periods created by expand_periods() are numbered from 0.

Usage

assign_stepped_wedge(
  data,
  cluster,
  period,
  waves,
  wave_length,
  start,
  lag = 0L,
  treatment = "treatment",
  transition = "transition",
  randomize = TRUE,
  seed = NULL
)

Arguments

data: Long-form base data.frame, or a simulab_sim, with one row per cluster unit and period and at least one row.
cluster: Cluster identifier. A single string naming a column of data, whose number of unique values must be divisible by waves.
period: Period variable. A single string naming a column of data, which must reach start + (waves - 1) * wave_length + lag.
waves: Number of waves. A single positive whole number.
wave_length: Periods between consecutive wave starts. A single positive whole number.
start: Treatment-start period of the first wave. A single number.
lag: Transition periods after a cluster's start before treatment becomes active. A single non-negative whole number, defaulting to 0.
treatment: Name of the active-treatment variable, which is 1 from treatment_start + lag onwards and 0 before. A single string, defaulting to "treatment".
transition: Name of the transition variable, which is 1 in the lag periods between a cluster's treatment_start and the start of active treatment. A single string, defaulting to "transition". The column is only added when lag is above 0.
randomize: Randomize the allocation of clusters to waves. A single flag, defaulting to TRUE. FALSE fills the waves in the order the clusters appear in data.
seed: Optional random seed. A single number, or NULL (the default).

Value

A simulab_sim base data.frame with the columns of data followed by the transition variable (only when lag is above 0) and the treatment variable, one row per input row. The component schedule, reached with as.data.frame(x, what = "schedule"), holds one row per cluster with the cluster identifier under its own name plus columns wave and treatment_start.

Examples

data <- expand_clusters(
  data.frame(cluster = 1:6), cluster = "cluster", size = 4
)
data <- expand_periods(data, periods = 5, id = "id", period = "period")

result <- assign_stepped_wedge(
  data, cluster = "cluster", period = "period",
  waves = 3, wave_length = 1, start = 2, seed = 1
)
head(result)
#> <simulab_sim:stepped_wedge> 6 rows x 5 columns
#>   id cluster period time treatment
#> 1  1       1      0    0         0
#> 2  1       1      1    1         0
#> 3  1       1      2    2         1
#> 4  1       1      3    3         1
#> 5  1       1      4    4         1
#> 6  2       1      0    0         0
#> 
#> Other tables: schedule. Read one with as.data.frame(x, what = "schedule").