derive_vars_dtm: Derive/Impute a Datetime from a Character Date

In admiral: ADaM in R Asset Library

Derive/Impute a Datetime from a Character Date

Description

Derive a datetime object (⁠*DTM⁠) from a character date (--DTC). The date and time can be imputed (see date_imputation/time_imputation arguments) and the date/time imputation flag (⁠*DTF⁠, ⁠*TMF⁠) can be added.

Usage

derive_vars_dtm(
  dataset,
  new_vars_prefix,
  dtc,
  highest_imputation = "h",
  date_imputation = "first",
  time_imputation = "first",
  flag_imputation = "auto",
  min_dates = NULL,
  max_dates = NULL,
  preserve = FALSE,
  ignore_seconds_flag = TRUE
)

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, for the date imputation flag (⁠*DTF⁠), and for the time imputation flag (⁠*TMF⁠), i.e., for new_vars_prefix = "AST" the variables ASTDT, ASTDTF, and ASTTMF 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" is specified, no imputation is performed, i.e., if any component is missing, NA_character_ is returned. If "Y" is specified, date_imputation should be "first" or "last" and min_dates or max_dates should be specified respectively. Otherwise, NA_character_ is returned if the year component is missing.
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).
time_imputation	The value to impute the time when a timepart is missing. A character value is expected, either as a format with hour, min and sec specified as "hh:mm:ss": e.g. "00:00:00" for the start of the day, or as a keyword: "first","last" to impute to the start/end of a day. The argument is ignored if highest_imputation = "n".
flag_imputation	Whether the date/time imputation flag(s) must also be derived. If "both" or "date" is specified, then date imputation flag is derived. If "auto" is specified and highest_imputation argument is greater than "h", then date imputation flag is derived. If "both" or "time" is specified, then time imputation flag is derived. If "auto" is specified and highest_imputation argument is not "n", then time imputation flag is derived. If "none" is specified, then no date or time imputation flag is derived. Please note that CDISC requirements dictate the need for a date/time 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_hm("2020-12-06T12:12"), ymd_hm("2020-11-11T11:11") ), 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). For date variables (not datetime) in the list the time is imputed to "00:00:00". Specifying date variables makes sense only if the date is imputed. If only time is imputed, date variables do not affect the result.
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. For date variables (not datetime) in the list the time is imputed to "23:59:59". Specifying date variables makes sense only if the date is imputed. If only time is imputed, date variables do not affect the result.
preserve	Preserve lower level date/time part when higher order part is missing, e.g. preserve day if month is missing or preserve minute when hour is missing. For example "2019---07" would return ⁠"2019-06-07⁠ if preserve = TRUE (and date_imputation = "mid").
ignore_seconds_flag	ADaM IG states that given SDTM (--DTC) variable, if only hours and minutes are ever collected, and seconds are imputed in (⁠*DTM⁠) as 00, then it is not necessary to set (⁠*TMF⁠) to "S". By default it is assumed that no seconds are collected and ⁠*TMF⁠ shouldn't be set to "S". A user can set this to FALSE if seconds are collected. The default value of ignore_seconds_flag is set to TRUE in admiral 1.4.0 and later.

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 the variable is not derived if it already exists in the input dataset. However, if ⁠*TMF⁠ already exists in the input dataset, a warning is issued and ⁠*TMF⁠ will be overwritten.

Value

The input dataset with the datetime ⁠*DTM⁠ (and the date/time imputation flag ⁠*DTF⁠, ⁠*TMF⁠) added.

See Also

vignette("imputation")

Date/Time Derivation Functions that returns variable appended to dataset: derive_var_trtdurd(), derive_vars_dt(), 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.