derive_vars_merged: Add New Variable(s) to the Input Dataset Based on Variables...

In admiral: ADaM in R Asset Library

Add New Variable(s) to the Input Dataset Based on Variables from Another Dataset

Description

Add new variable(s) to the input dataset based on variables from another dataset. The observations to merge can be selected by a condition (filter_add argument) and/or selecting the first or last observation for each by group (order and mode argument).

Usage

derive_vars_merged(
  dataset,
  dataset_add,
  by_vars,
  order = NULL,
  new_vars = NULL,
  filter_add = NULL,
  mode = NULL,
  exist_flag = NULL,
  true_value = "Y",
  false_value = NA_character_,
  missing_values = NULL,
  check_type = "warning",
  duplicate_msg = NULL,
  relationship = NULL
)

Arguments

dataset	Input dataset The variables specified by the by_vars argument are expected to be in the dataset. Permitted values a dataset, i.e., a data.frame or tibble Default value none
dataset_add	Additional dataset The variables specified by the by_vars, the new_vars, and the order argument are expected. Permitted values a dataset, i.e., a data.frame or tibble Default value none
by_vars	Grouping variables The input dataset and the selected observations from the additional dataset are merged by the specified variables. Variables can be renamed by naming the element, i.e. ⁠by_vars = exprs(<name in input dataset> = <name in additional dataset>)⁠, similar to the dplyr joins. Permitted values list of variables created by exprs(), e.g., exprs(USUBJID, VISIT) Default value none
order	Sort order If the argument is set to a non-null value, for each by group the first or last observation from the additional dataset is selected with respect to the specified order. Variables defined by the new_vars argument can be used in the sort order. For handling of NAs in sorting variables see Sort Order. Permitted values list of variables created by exprs(), e.g., exprs(USUBJID, VISIT) Default value NULL
new_vars	Variables to add The specified variables from the additional dataset are added to the output dataset. Variables can be renamed by naming the element, i.e., ⁠new_vars = exprs(<new name> = <old name>)⁠. For example new_vars = exprs(var1, var2) adds variables var1 and var2 from dataset_add to the input dataset. And new_vars = exprs(var1, new_var2 = old_var2) takes var1 and old_var2 from dataset_add and adds them to the input dataset renaming old_var2 to new_var2. Values of the added variables can be modified by specifying an expression. For example, new_vars = LASTRSP = exprs(str_to_upper(AVALC)) adds the variable LASTRSP to the dataset and sets it to the upper case value of AVALC. If the argument is not specified or set to NULL, all variables from the additional dataset (dataset_add) are added. In the case when a variable exists in both datasets, an error is issued to ensure the user either adds to by_vars, removes or renames. Permitted values list of variables created by exprs(), e.g., exprs(USUBJID, VISIT) Default value NULL
filter_add	Filter for additional dataset (dataset_add) Only observations fulfilling the specified condition are taken into account for merging. If the argument is not specified, all observations are considered. Variables defined by the new_vars argument can be used in the filter condition. Permitted values an unquoted condition, e.g., AVISIT == "BASELINE" Default value NULL
mode	Selection mode Determines if the first or last observation is selected. If the order argument is specified, mode must be non-null. If the order argument is not specified, the mode argument is ignored. Permitted values "first", "last" Default value NULL
exist_flag	Exist flag If the argument is specified (e.g., exist_flag = FLAG), the specified variable (e.g., FLAG) is added to the input dataset. This variable will be the value provided in true_value for all selected records from dataset_add which are merged into the input dataset, and the value provided in false_value otherwise. Permitted values an unquoted symbol, e.g., AVAL Default value NULL
true_value	True value The value for the specified variable exist_flag, applicable to the first or last observation (depending on the mode) of each by group. Permitted values a character scalar, i.e., a character vector of length one Default value "Y"
false_value	False value The value for the specified variable exist_flag, NOT applicable to the first or last observation (depending on the mode) of each by group. Permitted values a character scalar, i.e., a character vector of length one Default value NA_character_
missing_values	Values for non-matching observations For observations of the input dataset (dataset) which do not have a matching observation in the additional dataset (dataset_add) the values of the specified variables are set to the specified value. Only variables specified for new_vars can be specified for missing_values. Permitted values list of named expressions created by a formula using exprs(), e.g., exprs(AVALC = VSSTRESC, AVAL = yn_to_numeric(AVALC)) Default value NULL
check_type	Check uniqueness? If "warning", "message", or "error" is specified, the specified message is issued if the observations of the (restricted) additional dataset are not unique with respect to the by variables and the order. If the order argument is not specified, the check_type argument is ignored: if the observations of the (restricted) additional dataset are not unique with respect to the by variables, an error is issued. Permitted values "none", "message", "warning", "error" Default value "warning"
duplicate_msg	Message of unique check If the uniqueness check fails, the specified message is displayed. Permitted values a console message to be printed, e.g. "Attention" or for longer messages use paste("Line 1", "Line 2") Default value paste( "Dataset {.arg dataset_add} contains duplicate records with respect to", "{.var {vars2chr(by_vars)}}." )
relationship	Expected merge-relationship between the by_vars variable(s) in dataset (input dataset) and the dataset_add (additional dataset) containing the additional new_vars. This argument is passed to the dplyr::left_join() function. See https://dplyr.tidyverse.org/reference/mutate-joins.html#arguments for more details. Permitted values "one-to-one", "many-to-one" Default value NULL

Details

1. The new variables (new_vars) are added to the additional dataset (dataset_add).

2. The records from the additional dataset (dataset_add) are restricted to those matching the filter_add condition.

3. If order is specified, for each by group the first or last observation (depending on mode) is selected.

4. The variables specified for new_vars are merged to the input dataset using left_join(). I.e., the output dataset contains all observations from the input dataset. For observations without a matching observation in the additional dataset the new variables are set as specified by missing_values (or to NA for variables not in missing_values). Observations in the additional dataset which have no matching observation in the input dataset are ignored.

Value

The output dataset contains all observations and variables of the input dataset and additionally the variables specified for new_vars from the additional dataset (dataset_add).

Examples

Note on usage versus derive_vars_joined()

The question between using derive_vars_merged() or the more powerful derive_vars_joined() comes down to how you need to select the observations to be merged.

• If the observations from dataset_add to merge can be selected by a condition (filter_add) using only variables from dataset_add, then always use derive_vars_merged() as it requires less resources (time and memory). A common example of this would be a randomization date in ADSL, where you are simply merging on a date from DS according to a certain DSDECOD condition such as DSDECOD == "RANDOMIZATION".

• However, if the selection of the observations from dataset_add can depend on variables from both datasets, then use derive_vars_joined(). An example of this would be assigning period variables from ADSL to an ADAE, where you now need to check each adverse event start date against the period start and end dates to decide which period value to join.

Basic merge of a full dataset

Merge all demographic variables onto a vital signs dataset.

• The variable DOMAIN exists in both datasets so note the use of select(dm, -DOMAIN) in the dataset_add argument. Without this an error would be issued to notify the user.

library(tibble)
library(dplyr, warn.conflicts = FALSE)
vs <- tribble(
  ~DOMAIN,  ~USUBJID, ~VSTESTCD, ~VISIT,      ~VSSTRESN, ~VSDTC,
  "VS",     "01",     "HEIGHT",  "SCREENING",     178.0, "2013-08-20",
  "VS",     "01",     "WEIGHT",  "SCREENING",      81.9, "2013-08-20",
  "VS",     "01",     "WEIGHT",  "BASELINE",       82.1, "2013-08-29",
  "VS",     "01",     "WEIGHT",  "WEEK 2",         81.9, "2013-09-15",
  "VS",     "01",     "WEIGHT",  "WEEK 4",         82.6, "2013-09-24",
  "VS",     "02",     "WEIGHT",  "BASELINE",       58.6, "2014-01-11"
) %>%
  mutate(STUDYID = "AB42")

dm <- tribble(
  ~DOMAIN, ~USUBJID, ~AGE, ~AGEU,
  "DM",    "01",       61, "YEARS",
  "DM",    "02",       64, "YEARS",
  "DM",    "03",       85, "YEARS"
) %>%
  mutate(STUDYID = "AB42")

derive_vars_merged(
  vs,
  dataset_add = select(dm, -DOMAIN),
  by_vars = exprs(STUDYID, USUBJID)
) %>%
  select(USUBJID, VSTESTCD, VISIT, VSSTRESN, AGE, AGEU)
#> # A tibble: 6 × 6
#>   USUBJID VSTESTCD VISIT     VSSTRESN   AGE AGEU 
#>   <chr>   <chr>    <chr>        <dbl> <dbl> <chr>
#> 1 01      HEIGHT   SCREENING    178      61 YEARS
#> 2 01      WEIGHT   SCREENING     81.9    61 YEARS
#> 3 01      WEIGHT   BASELINE      82.1    61 YEARS
#> 4 01      WEIGHT   WEEK 2        81.9    61 YEARS
#> 5 01      WEIGHT   WEEK 4        82.6    61 YEARS
#> 6 02      WEIGHT   BASELINE      58.6    64 YEARS

Merge only the first/last value (order and mode)

Merge the last occurring weight for each subject to the demographics dataset.

• To enable sorting by visit date convert_dtc_to_dtm() is used to convert to a datetime, within the order argument.

• Then the mode argument is set to "last" to ensure the last sorted value is taken. Be cautious if NA values are possible in the order variables - see Sort Order.

• The filter_add argument is used to restrict the vital signs records only to weight assessments.

derive_vars_merged(
  dm,
  dataset_add = vs,
  by_vars = exprs(STUDYID, USUBJID),
  order = exprs(convert_dtc_to_dtm(VSDTC)),
  mode = "last",
  new_vars = exprs(LSTWT = VSSTRESN),
  filter_add = VSTESTCD == "WEIGHT"
) %>%
  select(USUBJID, AGE, AGEU, LSTWT)
#> # A tibble: 3 × 4
#>   USUBJID   AGE AGEU  LSTWT
#>   <chr>   <dbl> <chr> <dbl>
#> 1 01         61 YEARS  82.6
#> 2 02         64 YEARS  58.6
#> 3 03         85 YEARS  NA  

Handling duplicates (check_type)

The source records are checked regarding duplicates with respect to the by variables and the order specified. By default, a warning is issued if any duplicates are found. Note the results here with a new vital signs dataset containing a duplicate last weight assessment date.

vs_dup <- tribble(
  ~DOMAIN,  ~USUBJID, ~VSTESTCD, ~VISIT,      ~VSSTRESN, ~VSDTC,
  "VS",     "01",     "WEIGHT",  "WEEK 2",        81.1, "2013-09-24",
  "VS",     "01",     "WEIGHT",  "WEEK 4",        82.6, "2013-09-24"
) %>%
  mutate(STUDYID = "AB42")

derive_vars_merged(
  dm,
  dataset_add = vs_dup,
  by_vars = exprs(STUDYID, USUBJID),
  order = exprs(convert_dtc_to_dtm(VSDTC)),
  mode = "last",
  new_vars = exprs(LSTWT = VSSTRESN),
  filter_add = VSTESTCD == "WEIGHT"
) %>%
  select(USUBJID, AGE, AGEU, LSTWT)
#> # A tibble: 3 × 4
#>   USUBJID   AGE AGEU  LSTWT
#>   <chr>   <dbl> <chr> <dbl>
#> 1 01         61 YEARS  82.6
#> 2 02         64 YEARS  NA  
#> 3 03         85 YEARS  NA  
#> Warning: Dataset contains duplicate records with respect to `STUDYID`, `USUBJID`, and
#> `convert_dtc_to_dtm(VSDTC)`
#> i Run `admiral::get_duplicates_dataset()` to access the duplicate records

For investigating the issue, the dataset of the duplicate source records can be obtained by calling get_duplicates_dataset():

get_duplicates_dataset()
#> Duplicate records with respect to `STUDYID`, `USUBJID`, and
#> `convert_dtc_to_dtm(VSDTC)`.
#> # A tibble: 2 × 9
#>   STUDYID USUBJID convert_dtc_to_dtm(VSDT…¹ DOMAIN VSTESTCD VISIT VSSTRESN VSDTC
#> * <chr>   <chr>   <dttm>                    <chr>  <chr>    <chr>    <dbl> <chr>
#> 1 AB42    01      2013-09-24 00:00:00       VS     WEIGHT   WEEK…     81.1 2013…
#> 2 AB42    01      2013-09-24 00:00:00       VS     WEIGHT   WEEK…     82.6 2013…
#> # i abbreviated name: ¹`convert_dtc_to_dtm(VSDTC)`
#> # i 1 more variable: LSTWT <dbl>

Common options to solve the issue:

• Specifying additional variables for order - this is the most common approach, adding something like a sequence variable.

• Restricting the source records by specifying/updating the filter_add argument.

• Setting check_type = "none" to ignore any duplicates, but then in this case the last occurring record would be chosen according to the sort order of the input dataset_add. This is not often advisable, unless the order has no impact on the result, as the temporary sort order can be prone to variation across an ADaM script.

Modify values dependent on the merge (new_vars and missing_values)

For the last occurring weight for each subject, add a categorization of which visit it occurred at to the demographics dataset.

• In the new_vars argument, other functions can be utilized to modify the merged values. For example, in the below case we want to categorize the visit as "BASELINE" or "POST-BASELINE" using if_else().

• The missing_values argument assigns a specific value for subjects with no matching observations - see subject "03" in the below example.

derive_vars_merged(
  dm,
  dataset_add = vs,
  by_vars = exprs(STUDYID, USUBJID),
  order = exprs(convert_dtc_to_dtm(VSDTC)),
  mode = "last",
  new_vars = exprs(
    LSTWTCAT = if_else(VISIT == "BASELINE", "BASELINE", "POST-BASELINE")
  ),
  filter_add = VSTESTCD == "WEIGHT",
  missing_values = exprs(LSTWTCAT = "MISSING")
) %>%
  select(USUBJID, AGE, AGEU, LSTWTCAT)
#> # A tibble: 3 × 4
#>   USUBJID   AGE AGEU  LSTWTCAT     
#>   <chr>   <dbl> <chr> <chr>        
#> 1 01         61 YEARS POST-BASELINE
#> 2 02         64 YEARS BASELINE     
#> 3 03         85 YEARS MISSING      

Check existence of records to merge (exist_flag, true_value and false_value)

Similar to the above example, now we prefer to have a separate flag variable to show whether a selected record was merged.

• The name of the new variable is set with the exist_flag argument.

• The values of this new variable are assigned via the true_value and false_value arguments.

derive_vars_merged(
  dm,
  dataset_add = vs,
  by_vars = exprs(STUDYID, USUBJID),
  order = exprs(convert_dtc_to_dtm(VSDTC)),
  mode = "last",
  new_vars = exprs(
    LSTWTCAT = if_else(VISIT == "BASELINE", "BASELINE", "POST-BASELINE")
  ),
  filter_add = VSTESTCD == "WEIGHT",
  exist_flag = WTCHECK,
  true_value = "Y",
  false_value = "MISSING"
) %>%
  select(USUBJID, AGE, AGEU, LSTWTCAT, WTCHECK)
#> # A tibble: 3 × 5
#>   USUBJID   AGE AGEU  LSTWTCAT      WTCHECK
#>   <chr>   <dbl> <chr> <chr>         <chr>  
#> 1 01         61 YEARS POST-BASELINE Y      
#> 2 02         64 YEARS BASELINE      Y      
#> 3 03         85 YEARS <NA>          MISSING

Creating more than one variable from the merge (new_vars)

Derive treatment start datetime and associated imputation flags.

• In this example we first impute exposure datetime and associated flag variables as a separate first step to be used in the order argument.

• In the new_vars arguments, you can see how both datetime and the date and time imputation flags are all merged in one call.

ex <- tribble(
  ~DOMAIN, ~USUBJID, ~EXSTDTC,
  "EX",    "01",     "2013-08-29",
  "EX",    "01",     "2013-09-16",
  "EX",    "02",     "2014-01-11",
  "EX",    "02",     "2014-01-25"
) %>%
  mutate(STUDYID = "AB42")

ex_ext <- derive_vars_dtm(
  ex,
  dtc = EXSTDTC,
  new_vars_prefix = "EXST",
  highest_imputation = "M"
)
#> The default value of `ignore_seconds_flag` will change to "TRUE" in admiral
#> 1.4.0.

derive_vars_merged(
  dm,
  dataset_add = ex_ext,
  by_vars = exprs(STUDYID, USUBJID),
  new_vars = exprs(TRTSDTM = EXSTDTM, TRTSDTF = EXSTDTF, TRTSTMF = EXSTTMF),
  order = exprs(EXSTDTM),
  mode = "first"
) %>%
  select(USUBJID, TRTSDTM, TRTSDTF, TRTSTMF)
#> # A tibble: 3 × 4
#>   USUBJID TRTSDTM             TRTSDTF TRTSTMF
#>   <chr>   <dttm>              <chr>   <chr>  
#> 1 01      2013-08-29 00:00:00 <NA>    H      
#> 2 02      2014-01-11 00:00:00 <NA>    H      
#> 3 03      NA                  <NA>    <NA>   

Further examples

Further example usages of this function can be found in the Generic Derivations vignette.

See Also

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

admiral documentation built on June 26, 2025, 1:08 a.m.