derive_param_bmi: Adds a Parameter for BMI

In epijim/admiral: ADaM in R Asset Library

Description

Adds a record for BMI/Body Mass Index using Weight and Height each by group (e.g., subject and visit) where the source parameters are available.

Usage

derive_param_bmi(
  dataset,
  by_vars,
  set_values_to = vars(PARAMCD = "BMI"),
  weight_code = "WEIGHT",
  height_code = "HEIGHT",
  get_unit_expr,
  filter = NULL
)

Arguments

dataset	Input dataset The variables specified by the by_vars parameter, PARAMCD, and AVAL are expected. The variable specified by by_vars and PARAMCD must be a unique key of the input dataset after restricting it by the filter condition (filter parameter) and to the parameters specified by weight_code and height_code.
by_vars	Grouping variables For each group defined by by_vars an observation is added to the output dataset. Permitted Values: list of variables
set_values_to	Variables to be set The specified variables are set to the specified values for the new observations. For example vars(PARAMCD = "MAP") defines the parameter code for the new parameter. Permitted Values: List of variable-value pairs
weight_code	WEIGHT parameter code The observations where PARAMCD equals the specified value are considered as the WEIGHT. It is expected that WEIGHT is measured in kg Permitted Values: character value
height_code	HEIGHT parameter code The observations where PARAMCD equals the specified value are considered as the HEIGHT. It is expected that HEIGHT is measured in cm Permitted Values: character value
get_unit_expr	An expression providing the unit of the parameter The result is used to check the units of the input parameters. Permitted Values: A variable of the input dataset or a function call
filter	Filter condition The specified condition is applied to the input dataset before deriving the new parameter, i.e., only observations fulfilling the condition are taken into account. Permitted Values: a condition

Details

The analysis value of the new parameter is derived as

BMI = \frac{WEIGHT}{HEIGHT^2}

Value

The input dataset with the new parameter added

Author(s)

Pavan Kumar

Examples

advs <- tibble::tribble(
  ~USUBJID,      ~PARAMCD, ~PARAM,        ~AVAL, ~AVALU, ~AVISIT,
  "01-701-1015", "HEIGHT", "Height (cm)", 147,   "cm",   "SCREENING",
  "01-701-1015", "WEIGHT", "Weight (kg)", 54.0,  "kg",   "SCREENING",
  "01-701-1015", "WEIGHT", "Weight (kg)", 54.4,  "kg",   "BASELINE",
  "01-701-1015", "WEIGHT", "Weight (kg)", 53.1,  "kg",   "WEEK 2",
  "01-701-1028", "HEIGHT", "Height (cm)", 163,   "cm",   "SCREENING",
  "01-701-1028", "WEIGHT", "Weight (kg)", 78.5,  "kg",   "SCREENING",
  "01-701-1028", "WEIGHT", "Weight (kg)", 80.3,  "kg",   "BASELINE",
  "01-701-1028", "WEIGHT", "Weight (kg)", 80.7,  "kg",   "WEEK 2"
)

derive_param_bmi (
  advs,
  by_vars = vars(USUBJID, AVISIT),
  weight_code = "WEIGHT",
  height_code = "HEIGHT",
  set_values_to = vars(
    PARAMCD = "BMI",
    PARAM = "Body Mass Index (kg/m^2)"
  ),
  get_unit_expr = extract_unit(PARAM)
 )

epijim/admiral documentation built on Feb. 13, 2022, 12:15 a.m.