derive_var_extreme_flag: Add a Variable Flagging the First or Last Observation Within...

In admiral: ADaM in R Asset Library

Add a Variable Flagging the First or Last Observation Within Each By Group

Description

Add a variable flagging the first or last observation within each by group

Usage

derive_var_extreme_flag(
  dataset,
  by_vars,
  order,
  new_var,
  mode,
  true_value = "Y",
  false_value = NA_character_,
  flag_all = FALSE,
  check_type = "warning"
)

Arguments

dataset	Input dataset The variables specified by the by_vars argument are expected to be in the dataset.
by_vars	Grouping variables
order	Sort order The first or last observation is determined with respect to the specified order. For handling of NAs in sorting variables see the "Sort Order" section in vignette("generic").
new_var	Variable to add The specified variable is added to the output dataset. It is set to the value set in true_value for the first or last observation (depending on the mode) of each by group.
mode	Flag mode Determines of the first or last observation is flagged.
true_value	True value The value for the specified variable new_var, applicable to the first or last observation (depending on the mode) of each by group.
false_value	False value The value for the specified variable new_var, NOT applicable to the first or last observation (depending on the mode) of each by group.
flag_all	Flag setting A logical value where if set to TRUE, all records are flagged and no error or warning is issued if the first or last record is not unique.
check_type	Check uniqueness? If "warning" or "error" is specified, the specified message is issued if the observations of the input dataset are not unique with respect to the by variables and the order.

Details

For each group (with respect to the variables specified for the by_vars parameter), new_var is set to "Y" for the first or last observation (with respect to the order specified for the order parameter and the flag mode specified for the mode parameter). In the case where the user wants to flag multiple records of a grouping, for example records that all happen on the same visit and time, the argument flag_all can be set to TRUE. Otherwise, new_var is set to NA. Thus, the direction of "worst" is considered fixed for all parameters in the dataset depending on the order and the mode, i.e. for every parameter the first or last record will be flagged across the whole dataset.

Value

The input dataset with the new flag variable added

See Also

General Derivation Functions for all ADaMs that returns variable appended to dataset: derive_var_joined_exist_flag(), derive_var_merged_ef_msrc(), derive_var_merged_exist_flag(), derive_var_obs_number(), derive_var_relative_flag(), derive_vars_cat(), derive_vars_computed(), derive_vars_joined(), derive_vars_joined_summary(), derive_vars_merged(), derive_vars_merged_lookup(), derive_vars_merged_summary(), derive_vars_transposed()

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