Calculate a DY variable (day of study)

Utilizes the DY method from the SDTM spec: --DTC-RFSTDTC+1 if --DTC is on or after RFSTDTC. --DTC-RFSTDTC if --DTC precedes RFSTDTC. This function can also be used for the ENDY method from the spec which has the same logic.

Usage

calc_DY(tbl, DY_col, DTC_col, RFSTDTC = "RFSTDTC")

Arguments

tbl

a data frame with the date column RFSTDTC and the column specified by the DTC_col argument

DY_col

string, the name of the new DY column to create

DTC_col

string, the column in tbl which has the dates for which to calculated the DY value; should either already have a date class or be a character vector in the format YYYY-MM-DD

RFSTDTC

a string, the column to use for RFSTDTC, default is "RFSTDTC"; should either already have a date class or be a character vector in the format YYYY-MM-DD

Value

a modified copy of tbl with the new DY column

See also

create_BLFL(), create_EPOCH()

Examples

df <- data.frame(
  DTC = c("2023-08-01", "2023-08-02", "2023-08-03", "2023-08-04"),
  RFSTDTC = rep("2023-08-02", 4)
)
calc_DY(df, DY_col = "XXDY", DTC_col = "DTC")
#>          DTC    RFSTDTC XXDY
#> 1 2023-08-01 2023-08-02   -1
#> 2 2023-08-02 2023-08-02    1
#> 3 2023-08-03 2023-08-02    2
#> 4 2023-08-04 2023-08-02    3