derive_study_day performs study day calculation — derive_study

This function takes the an input data frame and a reference data frame (which is DM domain in most cases), and calculate the study day from reference date and target date. In case of unexpected conditions like reference date is not unique for each patient, or reference and input dates are not actual dates, NA will be returned for those records.

derive_study_day(
  sdtm_in,
  dm_domain,
  tgdt,
  refdt,
  study_day_var,
  merge_key = "USUBJID"
)

Arguments

sdtm_in: Input data frame that contains the target date.
dm_domain: Reference date frame that contains the reference date.
tgdt: Target date from sdtm_in that will be used to calculate the study day.
refdt: Reference date from dm_domain that will be used as reference to calculate the study day.
study_day_var: New study day variable name in the output. For example, AESTDY for AE domain and CMSTDY for CM domain.
merge_key: Character to represent the merging key between sdtm_in and dm_domain.

Value

Data frame that takes all columns from sdtm_in and a new variable to represent the calculated study day.

Examples

ae <- data.frame(
  USUBJID = c("study123-123", "study123-124", "study123-125"),
  AESTDTC = c("2012-01-01", "2012-04-14", "2012-04-14")
)
dm <- data.frame(
  USUBJID = c("study123-123", "study123-124", "study123-125"),
  RFSTDTC = c("2012-02-01", "2012-04-14", NA)
)
ae$AESTDTC <- as.Date(ae$AESTDTC)
dm$RFSTDTC <- as.Date(dm$RFSTDTC)
derive_study_day(ae, dm, "AESTDTC", "RFSTDTC", "AESTDY")
#>        USUBJID    AESTDTC AESTDY
#> 1 study123-123 2012-01-01    -31
#> 2 study123-124 2012-04-14      1
#> 3 study123-125 2012-04-14     NA