trapezoidal_linear_up_log_down: Linear-up and log-down trapezoidal rule

In nlmixr2autoinit: Automatic Generation of Initial Estimates for Population Pharmacokinetic Modeling

Linear-up and log-down trapezoidal rule

Description

Computes the area under the curve (AUC) or the area under the moment curve (AUMC) using a hybrid trapezoidal rule. The method uses linear interpolation for increasing or constant concentration segments, and logarithmic interpolation for decreasing segments.

Usage

trapezoidal_linear_up_log_down(x, y, moment = FALSE)

Arguments

x	A numeric vector representing the time points.
y	A numeric vector representing the corresponding concentration values at each time point.
moment	Logical. If TRUE, computes AUMC by integrating t * C(t) instead of C(t).

Details

If moment = TRUE, the function calculates the area under the moment curve (AUMC), i.e., it integrates t * C(t) over time instead of just C(t).

Value

A numeric value representing the estimated AUC or AUMC using the linear-up/log-down trapezoidal method.

Examples

x <- c(0, 0.5, 1, 2, 4, 6, 8)
y <- c(0, 2, 8, 5, 3, 2, 1)
trapezoidal_linear_up_log_down(x, y)                # AUC
trapezoidal_linear_up_log_down(x, y, moment = TRUE) # AUMC

nlmixr2autoinit documentation built on Nov. 14, 2025, 1:07 a.m.