last 3 time points [🇷 for BE/BA]

posted by martin  – Austria, 2008-10-12 02:04 (6450 d 02:37 ago) – Posting: # 2519
Views: 26,353

dear Yung-jin Lee !

good to hear that your code will be much more sophisticated than WinNonLin! I appreciate your efforts. you may find of interest that in the case of manual selection of the last 3 time points, the middle time point is “useless” to calculate lambda_z by using the OLS fitting criteria in the case of equidistant measurement time points. in this case, the middle data tuple only effects the intercept but not the slope (=lambda_z). you may think about implementing a warning message in this case.

the theoretical background for this unexpected behavior rather complicated but I can provide you some information upon request.

some examples:
t <- c(10, 12, 14) # equidistant time points
c1 <- c(5, 4, 1)
c2 <- rnorm(3)
c3 <- runif(3)

lm(c1~t)
lm(c1[-2]~t[-2])

lm(c2~t)
lm(c2[-2]~t[-2])

lm(c3~t)
lm(c3[-2]~t[-2])

Complete thread:

UA Flag
Activity
 Admin contact
23,653 posts in 4,991 threads, 1,570 registered users;
116 visitors (0 registered, 116 guests [including 22 identified bots]).
Forum time: 04:42 CEST (Europe/Vienna)

In theory, there is no difference between theory and practice.
But, in practice, there is.    Jan L.A. van de Snepscheut

The Bioequivalence and Bioavailability Forum is hosted by
BEBAC Ing. Helmut Schütz
HTML5