BestSlope: Choose the best-fit slope for the log(y) and x regression by...

In asancpt/NonCompart: Noncompartmental Analysis for Pharmacokinetic Data

Choose the best-fit slope for the log(y) and x regression by the criteria of adjusted R-square.

Description

It sequentially fits (log(y) ~ x) from the last point of x to the previous points with at least 3 points. It chooses a slope the highest adjusted R-square. If the difference is less then 1e-4, it pickes longer slope.

Usage

  BestSlope(x, y, adm = "Extravascular", TOL=1e-4, excludeDelta = 1)

Arguments

x	vector values of x-axis, usually time
y	vector values of y-axis, usually concentration
adm	one of "Bolus" or "Infusion" or "Extravascular" to indicate drug administration mode
TOL	tolerance. See Phoneix WinNonlin 6.4 User's Guide p33 for the detail.
excludeDelta	Improvement of R2ADJ larger than this value could exclude the last point. Default value 1 is for the compatibility with other software.

Details

Choosing the best terminal slope (y in log scale) in pharmacokinetic analysis is somewhat challenging, and it could vary by analysis performer. Pheonix WinNonlin chooses a slope with highest adjusted R-squared and the longest one. The difference of adjusted R-Squared less than TOL considered to be 0. This function uses ordinary least square method (OLS). Author recommends to use excludeDelta option with about 0.3.

Value

R2	R-squared
R2ADJ	adjusted R-squared
LAMZNPT	number of points used for slope
LAMZ	negative of the slope, lambda_z
b0	intercept of the regression line
CORRXY	correlation of log(y) and x
LAMZLL	earliest x for lambda_z
LAMZUL	last x for lambda_z
CLSTP	predicted y value at the last point, predicted concentration for the last time point

Author(s)

Kyun-Seop Bae <[e-mail]>

See Also

Slope

Examples

BestSlope(Theoph[Theoph$Subject==1, "Time"], Theoph[Theoph$Subject==1, "conc"])
BestSlope(Indometh[Indometh$Subject==1, "time"], Indometh[Indometh$Subject==1, "conc"],
          adm="Bolus")

asancpt/NonCompart documentation built on Sept. 6, 2022, 6:47 a.m.