Title: Utility Functions to Support and Extend the 'rbmi' Package
Version: 0.1.4
Description: Provides utility functions that extend the capabilities of the reference-based multiple imputation package 'rbmi'. It supports clinical trial analysis workflows with functions for managing imputed datasets, applying analysis methods across imputations, and tidying results for reporting.
Maintainer: Mark Baillie <bailliem@gmail.com>
License: GPL (≥ 3)
Encoding: UTF-8
RoxygenNote: 7.3.2
Suggests: knitr, rmarkdown, spelling, testthat (≥ 3.0.0), tidyr, readr, tibble, ggplot2, rstan
Config/testthat/edition: 3
Language: en-US
Imports: assertthat, dplyr, purrr, rbmi (≥ 1.4), beeca, rlang
VignetteBuilder: knitr
Depends: R (≥ 4.1)
LazyData: true
URL: https://github.com/openpharma/rbmiUtils
BugReports: https://github.com/openpharma/rbmiUtils/issues
NeedsCompilation: no
Packaged: 2025-05-20 19:32:01 UTC; bailliem
Author: Mark Baillie ORCID iD [aut, cre, cph], Tobias Mütze ORCID iD [aut], Jack Talboys [aut], Lukas A. Widmer ORCID iD [ctb]
Repository: CRAN
Date/Publication: 2025-05-23 18:32:01 UTC

rbmiUtils: Utility Functions to Support and Extend the 'rbmi' Package

Description

Provides utility functions that extend the capabilities of the reference-based multiple imputation package 'rbmi'. It supports clinical trial analysis workflows with functions for managing imputed datasets, applying analysis methods across imputations, and tidying results for reporting.

Author(s)

Maintainer: Mark Baillie bailliem@gmail.com (ORCID) [copyright holder]

Authors:

Other contributors:

See Also

Useful links:

Example efficacy trial dataset

Description

A simplified example of a simulated trial dataset, with missing data.

Usage

ADEFF

Format

ADEFF A data frame with 1,000 rows and 10 columns:

USUBJID

Unique subject identifier

AVAL

Primary outcome variable

TRT01P

Planned treatment

STRATA

Stratification at randomisation

REGION

Stratification by region

REGIONC

Stratification by region, numeric code

BASE

Baseline value of primary outcome variable

CHG

Change from baseline

AVISIT

Visit number

PARAM

Analysis parameter name

Example multiple imputation trial dataset

Description

A simplified example of a simulated trial ADMI dataset

Usage

ADMI

Format

ADMI A data frame with 100,000 rows and 12 columns:

USUBJID

Unique patient identifier

STRATA

Stratification at randomisation

REGION

Stratification by region

REGIONC

Stratification by region, numeric code

TRT

Planned treatment

BASE

Baseline value of primary outcome variable

CHG

Change from baseline

AVISIT

Visit number

IMPID

Imputation number identifier

CRIT1FLN

Responder criteria (binary)

CRIT1FL

Responder criteria (categorical)

CRIT

Responder criteria (definition)

Apply Analysis Function to Multiple Imputed Datasets

Description

This function applies an analysis function (e.g., ANCOVA) to imputed datasets and stores the results for later pooling. It is designed to work with multiple imputed datasets and apply a given analysis function to each imputation iteration.

Usage

analyse_mi_data(
  data = NULL,
  vars = NULL,
  method = NULL,
  fun = rbmi::ancova,
  delta = NULL,
  ...
)

Arguments

data

A data frame containing the imputed datasets. The data frame should include a variable (e.g., IMPID) that identifies distinct imputation iterations.

vars

A list specifying key variables used in the analysis (e.g., subjid, visit, group, outcome). Required.

method

A character string or object specifying the method used for analysis (e.g., Bayesian imputation). Defaults to NULL.

fun

A function that will be applied to each imputed dataset. Defaults to rbmi::ancova. Must be a valid analysis function.

delta

A data.frame used for delta adjustments, or NULL if no delta adjustments are needed. Defaults to NULL.

...

Additional arguments passed to the analysis function fun.

Details

The function loops through distinct imputation datasets (identified by IMPID), applies the provided analysis function fun, and stores the results for later pooling. If a delta dataset is provided, it will be merged with the imputed data to apply the specified delta adjustment before analysis.

Value

An object of class analysis containing the results from applying the analysis function to each imputed dataset.

Examples

# Example usage with an ANCOVA function
library(dplyr)
library(rbmi)
library(rbmiUtils)
set.seed(123)
data("ADMI")

# Convert key columns to factors
ADMI$TRT <- factor(ADMI$TRT, levels = c("Placebo", "Drug A"))
ADMI$USUBJID <- factor(ADMI$USUBJID)
ADMI$AVISIT <- factor(ADMI$AVISIT)

# Define key variables for ANCOVA analysis
 vars <- set_vars(
  subjid = "USUBJID",
  visit = "AVISIT",
  group = "TRT",
  outcome = "CHG",
  covariates = c("BASE", "STRATA", "REGION")  # Covariates for adjustment
 )

# Specify the imputation method (Bayesian) - need for pool step
 method <- rbmi::method_bayes(
 n_samples = 20,
 control = rbmi::control_bayes(
   warmup = 20,
   thin = 1
   )
 )

# Perform ANCOVA Analysis on Each Imputed Dataset
ana_obj_ancova <- analyse_mi_data(
  data = ADMI,
  vars = vars,
  method = method,
  fun = ancova,  # Apply ANCOVA
  delta = NULL   # No sensitivity analysis adjustment
)

Construct an rbmi analysis object

Description

This is a helper function to create an analysis object that stores the results from multiple imputation analyses. It validates the results and ensures proper class assignment.

This is a modification of the rbmi::as_analysis function.

Usage

as_analysis2(results, method, delta = NULL, fun = NULL, fun_name = NULL)

Arguments

results

A list containing the analysis results for each imputation.

method

The method object used for the imputation.

delta

Optional. A delta dataset used for adjustment.

fun

The analysis function that was used.

fun_name

The name of the analysis function (used for printing).

Value

An object of class analysis with the results and associated metadata.

Convert character variable list to formula

Description

Convert character variable list to formula

Usage

as_simple_formula2(outcome, covars)

Arguments

outcome

Character string, the outcome variable.

covars

Character vector of covariates.

Value

A formula object.

Extract variable names from model terms

Description

Takes a character vector including potentially model terms like * and : and extracts out the individual variables.

Usage

extract_covariates2(x)

Arguments

x

A character vector of model terms.

Value

A character vector of unique variable names.

Utility function for Generalized G-computation for Binary Outcomes

Description

Wrapper function for targeting a marginal treatment effect using g-computation using the beeca package. Intended for binary endpoints.

Usage

gcomp_binary(
  data,
  outcome = "CRIT1FLN",
  treatment = "TRT",
  covariates = c("BASE", "STRATA", "REGION"),
  reference = "Placebo",
  contrast = "diff",
  method = "Ge",
  type = "HC0",
  ...
)

Arguments

data

A data.frame containing the analysis dataset.

outcome

Name of the binary outcome variable (as string).

treatment

Name of the treatment variable (as string).

covariates

Character vector of covariate names to adjust for.

reference

Reference level for the treatment variable (default: "Placebo").

contrast

Type of contrast to compute (default: "diff").

method

Marginal estimation method for variance (default: "Ge").

type

Variance estimator type (default: "HC0").

...

Additional arguments passed to beeca::get_marginal_effect().

Value

A named list with treatment effect estimate, standard error, and degrees of freedom (if applicable).

Examples

# Load required packages
library(rbmiUtils)
library(beeca)      # for get_marginal_effect()
library(dplyr)
# Load example data
data("ADMI")
# Ensure correct factor levels
ADMI <- ADMI %>%
  mutate(
    TRT = factor(TRT, levels = c("Placebo", "Drug A")),
    STRATA = factor(STRATA),
    REGION = factor(REGION)
  )
# Apply g-computation for binary responder
result <- gcomp_binary(
  data = ADMI,
  outcome = "CRIT1FLN",
  treatment = "TRT",
  covariates = c("BASE", "STRATA", "REGION"),
  reference = "Placebo",
  contrast = "diff",
  method = "Ge",    # from beeca: GEE robust sandwich estimator
  type = "HC0"      # from beeca: heteroskedasticity-consistent SE
)

# Print results
print(result)

G-computation Analysis for a Single Visit

Description

Performs logistic regression and estimates marginal effects for binary outcomes.

Usage

gcomp_responder(
  data,
  vars,
  reference_levels = NULL,
  var_method = "Ge",
  type = "HC0",
  contrast = "diff"
)

Arguments

data

A data.frame with one visit of data.

vars

A list containing group, outcome, covariates, and visit.

reference_levels

Optional vector specifying reference level(s) of the treatment factor.

var_method

Marginal variance estimation method (default: "Ge").

type

Type of robust variance estimator (default: "HC0").

contrast

Type of contrast to compute (default: "diff").

Value

A named list containing estimates and standard errors for treatment comparisons and within-arm means.

G-computation for a Binary Outcome at Multiple Visits

Description

Applies gcomp_responder() separately for each unique visit in the data.

Usage

gcomp_responder_multi(data, vars, reference_levels = NULL, ...)

Arguments

data

A data.frame containing multiple visits.

vars

A list specifying analysis variables.

reference_levels

Optional reference level for the treatment variable.

...

Additional arguments passed to gcomp_responder().

Value

A named list of estimates for each visit and treatment group.

Examples


library(dplyr)
library(rbmi)
library(rbmiUtils)

data("ADMI")

ADMI <- ADMI |>
  mutate(
    TRT = factor(TRT, levels = c("Placebo", "Drug A")),
    STRATA = factor(STRATA),
    REGION = factor(REGION)
  )

# Note: method must match the original used for imputation
method <- method_bayes(
  n_samples = 100,
  control = control_bayes(warmup = 20, thin = 2)
)

vars_binary <- set_vars(
  subjid = "USUBJID",
  visit = "AVISIT",
  group = "TRT",
  outcome = "CRIT1FLN",
  covariates = c("BASE", "STRATA", "REGION")
)

ana_obj_prop <- analyse_mi_data(
  data = ADMI,
  vars = vars_binary,
  method = method,
  fun = gcomp_responder_multi,
  reference_levels = "Placebo",
  contrast = "diff",
  var_method = "Ge",
  type = "HC0"
)

pool(ana_obj_prop)

Get Imputed Data Sets as a data frame

Description

This function takes an imputed dataset and a mapping variable to return a dataset with the original IDs mapped back and renamed appropriately.

Usage

get_imputed_data(impute_obj)

Arguments

impute_obj

The imputation object from which the imputed datasets are extracted.

Value

A data frame with the original subject IDs mapped and renamed.

Examples


library(dplyr)
library(rbmi)
library(rbmiUtils)

set.seed(1974)
# Load example dataset
data("ADEFF")

# Prepare data
ADEFF <- ADEFF |>
  mutate(
    TRT = factor(TRT01P, levels = c("Placebo", "Drug A")),
    USUBJID = factor(USUBJID),
    AVISIT = factor(AVISIT)
  )

# Define variables for imputation
vars <- set_vars(
  subjid = "USUBJID",
  visit = "AVISIT",
  group = "TRT",
  outcome = "CHG",
  covariates = c("BASE", "STRATA", "REGION")
)

# Define Bayesian imputation method
method <- method_bayes(
  n_samples = 100,
  control = control_bayes(warmup = 200, thin = 2)
)

# Generate draws and perform imputation
draws_obj <- draws(data = ADEFF, vars = vars, method = method)
impute_obj <- impute(draws_obj,
  references = c("Placebo" = "Placebo", "Drug A" = "Placebo"))

# Extract imputed data with original subject IDs
admi <- get_imputed_data(impute_obj)
head(admi)

Tidy and Annotate a Pooled Object for Publication

Description

This function processes a pooled analysis object of class pool into a tidy tibble format. It adds contextual information, such as whether a parameter is a treatment comparison or a least squares mean, dynamically identifies visit names from the parameter column, and provides additional columns for parameter type, least squares mean type, and visit.

Usage

tidy_pool_obj(pool_obj)

Arguments

pool_obj

A pooled analysis object of class pool.

Details

The function rounds numeric columns to three decimal places for presentation. It dynamically processes the parameter column by separating it into components (e.g., type of estimate, reference vs. alternative arm, and visit), and provides informative descriptions in the output.

Value

A tibble containing the processed pooled analysis results. The tibble includes columns for the parameter, description, estimates, standard errors, confidence intervals, p-values, visit, parameter type, and least squares mean type.

Examples

# Example usage:
library(dplyr)
library(rbmi)

data("ADMI")
N_IMPUTATIONS <- 100
BURN_IN <- 200
BURN_BETWEEN <- 5

# Convert key columns to factors
ADMI$TRT <- factor(ADMI$TRT, levels = c("Placebo", "Drug A"))
ADMI$USUBJID <- factor(ADMI$USUBJID)
ADMI$AVISIT <- factor(ADMI$AVISIT)

# Define key variables for ANCOVA analysis
 vars <- set_vars(
  subjid = "USUBJID",
  visit = "AVISIT",
  group = "TRT",
  outcome = "CHG",
  covariates = c("BASE", "STRATA", "REGION")  # Covariates for adjustment
 )

# Specify the imputation method (Bayesian) - need for pool step
method <- rbmi::method_bayes(
  n_samples = N_IMPUTATIONS,
  control = rbmi::control_bayes(
    warmup = BURN_IN,
    thin = BURN_BETWEEN
    )
  )

# Perform ANCOVA Analysis on Each Imputed Dataset
ana_obj_ancova <- analyse_mi_data(
  data = ADMI,
  vars = vars,
  method = method,
  fun = ancova,  # Apply ANCOVA
  delta = NULL   # No sensitivity analysis adjustment
)

pool_obj_ancova <- pool(ana_obj_ancova)
tidy_df <- tidy_pool_obj(pool_obj_ancova)

# Print tidy data frames
print(tidy_df)

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