Still can't make it work [R for BE/BA]

posted by ElMaestro  – Denmark, 2020-08-07 11:08 (282 d 09:18 ago) – Posting: # 21831
Views: 7,988
(edited by ElMaestro on 2020-08-07 11:25)

Hi PharmCat,

thanks for trying to assist on this. :-) It is kind of you.

» I think Xi is not shuld be full-rank design matrix. It is just part of X for subject i. Moreover all Xi should be the same width (num of columns) for Σ(Xi'V-1Xi). Also with (yi - Xi*β) you get residuals ri (col num of Xi should be equal length β).
» There is not very accurate description in Gurka's paper, but it provide good concept.
» If you check, it should work.
I can't make it work.
In Gurka's equation 3, where we can write the shorthand beta= M1-1*M2: When using the little 3-by-6 matrices for Xi, M1 becomes non-invertible.
I tried to lump 6 subjects together at a time, and now I am getting an estimate of beta but it appears wrong, in the sense it is not corresponding to what I get for the full model.

I wonder if Gurka's equation only works under assumptions not mentioned in the paper or if I am just a very lousy programmer. My money is clearly on the latter :-D
—
Pass or fail!
ElMaestro

Complete thread:

Activity
 Admin contact
21,462 posts in 4,487 threads, 1,514 registered users;
online 11 (0 registered, 11 guests [including 3 identified bots]).
Forum time: Sunday 20:26 UTC (Europe/Vienna)

Pharmacokinetics may be simply defined as
what the body does to the drug,
as opposed to pharmacodynamics, which may be defined as
what the drug does to the body.    Leslie Z. Benet

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