Derive Relative Day Variables

Adds relative day variables (--DY) to the dataset, e.g., ASTDY and AENDY.

derive_vars_dy(dataset, reference_date, source_vars)

Arguments

dataset

Input dataset

The variables specified by the reference_date and source_vars arguments are expected to be in the dataset.

Default value

none

reference_date

A date or date-time column, e.g., date of first treatment or date-time of last exposure to treatment.

Refer to derive_vars_dt() to impute and derive a date from a date character vector to a date object.

Default value

none

source_vars

A list of datetime or date variables created using exprs() from which dates are to be extracted. This can either be a list of date(time) variables or named --DY variables and corresponding –DT(M) variables e.g. exprs(TRTSDTM, ASTDTM, AENDT) or exprs(TRTSDT, ASTDTM, AENDT, DEATHDY = DTHDT). If the source variable does not end in –DT(M), a name for the resulting --DY variable must be provided.

Default value

none

Value

The input dataset with --DY corresponding to the --DTM or --DT source variable(s) added

Details

The relative day is derived as number of days from the reference date to the end date. If it is nonnegative, one is added. I.e., the relative day of the reference date is 1. Unless a name is explicitly specified, the name of the resulting relative day variable is generated from the source variable name by replacing DT (or DTM as appropriate) with DY.

See also

Date/Time Derivation Functions that returns variable appended to dataset: derive_var_trtdurd(), derive_vars_dt(), derive_vars_dtm(), derive_vars_dtm_to_dt(), derive_vars_dtm_to_tm(), derive_vars_duration()

Examples

library(tibble)
library(lubridate)
library(dplyr, warn.conflicts = FALSE)

datain <- tribble(
  ~TRTSDTM, ~ASTDTM, ~AENDT,
  "2014-01-17T23:59:59", "2014-01-18T13:09:O9", "2014-01-20"
) %>%
  mutate(
    TRTSDTM = as_datetime(TRTSDTM),
    ASTDTM = as_datetime(ASTDTM),
    AENDT = ymd(AENDT)
  )

derive_vars_dy(
  datain,
  reference_date = TRTSDTM,
  source_vars = exprs(TRTSDTM, ASTDTM, AENDT)
)
#> # A tibble: 1 × 6
#>   TRTSDTM             ASTDTM              AENDT      TRTSDY ASTDY AENDY
#>   <dttm>              <dttm>              <date>      <dbl> <dbl> <dbl>
#> 1 2014-01-17 23:59:59 2014-01-18 13:09:09 2014-01-20      1     2     4

# specifying name of new variables
datain <- tribble(
  ~TRTSDT, ~DTHDT,
  "2014-01-17", "2014-02-01"
) %>%
  mutate(
    TRTSDT = ymd(TRTSDT),
    DTHDT = ymd(DTHDT)
  )

derive_vars_dy(
  datain,
  reference_date = TRTSDT,
  source_vars = exprs(TRTSDT, DEATHDY = DTHDT)
)
#> # A tibble: 1 × 4
#>   TRTSDT     DTHDT      TRTSDY DEATHDY
#>   <date>     <date>      <dbl>   <dbl>
#> 1 2014-01-17 2014-02-01      1      16