nlmixr2auto (version 1.0.0)

initialize_param_table: Generate initial parameter table for pharmacometric model estimation

Description

Creates a structured parameter table containing initial estimates with constraints for base parameters, inter-individual variability (ETA), residual errors (SIGMA), and correlation terms (OMEGA) to initialize nonlinear mixed-effects model fitting.

Usage

initialize_param_table()

Value

A data.frame with 29 columns containing parameter specifications. The structure includes:

Name

Parameter name (e.g., "lcl", "eta.vc", "cor.eta_cl_vc")

init

Numeric initial value for parameter estimation

lb

Lower bound constraint (use -Inf for unconstrained)

ub

Upper bound constraint (use Inf for unconstrained)

fixed

Integer flag indicating whether parameter should be fixed (1) or estimated (0)

Description

Text description of parameter's biological/pharmacometric meaning

Author

Zhonghui Huang

Details

This table includes:

• Base PK parameters (absorption, clearance, volumes, etc.) in log-scale

• Michaelis-Menten kinetics parameters (vmax, km)

• Absorption parameters including zero-order, mixed-order, and transit compartment models

• Residual variability components (additive and proportional error)

• Inter-individual variability (ETA) terms with variance parameters

• Correlation parameters between ETA terms in two blocks:

  • Block 1: vmax and km parameters

  • Block 2: clearance, volumes, and inter-compartmental clearance

Parameters are organized with:

• Name: Parameter name following standard nomenclature

• init: Initial estimate for model fitting

• lb/ub: Lower/upper bounds for parameter estimation

• fixed: Flag indicating fixed parameters (1) vs estimated (0)

• Description: Plain-text explanation of parameter meaning

Examples

# Generate default parameter table
initialize_param_table()