Not understood [R for BE/BA]

posted by PharmCat  – Russia, 2020-08-05 01:41 (172 d 15:12 ago) – Posting: # 21823
Views: 7,171

» Can you describe what you meant?


Hello ElMaestro!

logREML of all data is just sum of individual subject logREML. See Mary J. Lindstrom and Douglas M. Bates, Newton-Raphson and EM Algorithms for Linear Mixed-Effects Models for Repeated-Measures Data.

You can make big sparce V matrix for all data and then inverce it (solve(CovM) in your code above) or you can take indiviual Xi and Vi and calculate logREML for each subject and sum.

Problem1: when you have big matrix invercing is slow as hell, but if you inverce by blocks (you can do it because it block-diagonal) it can be done faster.

Problem2: In BE case you have many equal Zi matrices, so in logREML calculation (if you calc by subject) you inverce one matrix many times (because V = ZGZ'+R, Z can be different, G and R not changing subject by subject). If you cache result - you can seriously increase performance.

So, I didn't read all R code (sorry) and I didn't understand what approach is used.

Complete thread:

Activity
 Admin contact
21,310 posts in 4,445 threads, 1,489 registered users;
online 3 (0 registered, 3 guests [including 2 identified bots]).
Forum time: Sunday 15:54 CET (Europe/Vienna)

Every man gets a narrower and narrower field of knowledge
in which he must be an expert in order to compete with other people.
The specialist knows more and more about less and less
and finally knows everything about nothing.    Konrad Lorenz

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