emp_start: Empirical Starting Value

In mmrm: Mixed Models for Repeated Measures

Empirical Starting Value

Description

Obtain empirical start value for unstructured covariance

Usage

emp_start(data, model_formula, visit_var, subject_var, subject_groups, ...)

Arguments

data	(data.frame) data used for model fitting.
model_formula	(formula) the formula in mmrm model without covariance structure part.
visit_var	(string) visit variable.
subject_var	(string) subject id variable.
subject_groups	(factor) subject group assignment.
...	not used.

Details

This emp_start only works for unstructured covariance structure. It uses linear regression to first obtain the coefficients and use the residuals to obtain the empirical variance-covariance, and it is then used to obtain the starting values.

Value

A numeric vector of starting values.

Note

data is used instead of full_frame because full_frame is already transformed if model contains transformations, e.g. log(FEV1) ~ exp(FEV1_BL) will drop FEV1 and FEV1_BL but add log(FEV1) and exp(FEV1_BL) in full_frame.

mmrm documentation built on Oct. 7, 2024, 1:14 a.m.