derive_vars_dt: Derive/Impute a Date from a Character Date

In admiral: ADaM in R Asset Library

Derive/Impute a Date from a Character Date

Description

Derive a date (⁠*DT⁠) from a character date (--DTC). The date can be imputed (see date_imputation argument) and the date imputation flag (⁠*DTF⁠) can be added.

Usage

derive_vars_dt(
  dataset,
  new_vars_prefix,
  dtc,
  highest_imputation = "n",
  date_imputation = "first",
  flag_imputation = "auto",
  min_dates = NULL,
  max_dates = NULL,
  preserve = FALSE
)

Arguments

dataset	Input dataset The variables specified by the dtc argument are expected to be in the dataset.
new_vars_prefix	Prefix used for the output variable(s). A character scalar is expected. For the date variable (⁠*DT⁠) is appended to the specified prefix and for the date imputation flag (⁠*DTF⁠), i.e., for new_vars_prefix = "AST" the variables ASTDT and ASTDTF are created.
dtc	The --DTC date to impute A character date is expected in a format like yyyy-mm-dd or yyyy-mm-ddThh:mm:ss. Trailing components can be omitted and - is a valid "missing" value for any component.
highest_imputation	Highest imputation level The highest_imputation argument controls which components of the --DTC value are imputed if they are missing. All components up to the specified level are imputed. If a component at a higher level than the highest imputation level is missing, NA_character_ is returned. For example, for highest_imputation = "D" "2020" results in NA_character_ because the month is missing. If "n" (none, lowest level) is specified no imputation is performed, i.e., if any component is missing, NA_character_ is returned. If "Y" (year, highest level) is specified, date_imputation must be "first" or "last" and min_dates or max_dates must be specified respectively. Otherwise, an error is thrown.
date_imputation	The value to impute the day/month when a datepart is missing. A character value is expected. If highest_imputation is "M", month and day can be specified as "mm-dd": e.g. "06-15" for the 15th of June When highest_imputation is "M" or "D", the following keywords are available: "first", "mid", "last" to impute to the first/mid/last day/month. If "mid" is specified, missing components are imputed as the middle of the possible range: If both month and day are missing, they are imputed as "06-30" (middle of the year). If only day is missing, it is imputed as "15" (middle of the month). The year can not be specified; for imputing the year "first" or "last" together with min_dates or max_dates argument can be used (see examples).
flag_imputation	Whether the date imputation flag must also be derived. If "auto" is specified and highest_imputation argument is not "n", then date imputation flag is derived. If "date" is specified, then date imputation flag is derived. If "none" is specified, then no date imputation flag is derived. Please note that CDISC requirements dictate the need for a date imputation flag if any imputation is performed, so flag_imputation = "none" should only be used if the imputed variable is not part of the final ADaM dataset.
min_dates	Minimum dates A list of dates is expected. It is ensured that the imputed date is not before any of the specified dates, e.g., that the imputed adverse event start date is not before the first treatment date. Only dates which are in the range of possible dates of the dtc value are considered. The possible dates are defined by the missing parts of the dtc date (see example below). This ensures that the non-missing parts of the dtc date are not changed. A date or date-time object is expected. For example impute_dtc_dtm( "2020-11", min_dates = list( ymd_hms("2020-12-06T12:12:12"), ymd_hms("2020-11-11T11:11:11") ), highest_imputation = "M" ) returns "2020-11-11T11:11:11" because the possible dates for "2020-11" range from "2020-11-01T00:00:00" to "2020-11-30T23:59:59". Therefore "2020-12-06T12:12:12" is ignored. Returning "2020-12-06T12:12:12" would have changed the month although it is not missing (in the dtc date).
max_dates	Maximum dates A list of dates is expected. It is ensured that the imputed date is not after any of the specified dates, e.g., that the imputed date is not after the data cut off date. Only dates which are in the range of possible dates are considered. A date or date-time object is expected.
preserve	Preserve day if month is missing and day is present For example "2019---07" would return ⁠"2019-06-07⁠ if preserve = TRUE (and date_imputation = "MID").

Details

In {admiral} we don't allow users to pick any single part of the date/time to impute, we only enable to impute up to a highest level, i.e. you couldn't choose to say impute months, but not days.

The presence of a ⁠*DTF⁠ variable is checked and if it already exists in the input dataset, a warning is issued and ⁠*DTF⁠ will be overwritten.

Value

The input dataset with the date ⁠*DT⁠ (and the date imputation flag ⁠*DTF⁠ if requested) added.

See Also

vignette("imputation")

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

admiral documentation built on May 28, 2026, 9:08 a.m.