Re: permissible band matrix

OMEGA matrix should be positive definite, and the one that you use is not of this class: > b <- 7 > a <- 9 > b1 <- 7 > aa <- matrix(c(a,b1,0,0,b1,a,b,0,0,b,a,b1,0,0,b1,a),4,4) > aa [,1] [,2] [,3] [,4] [1,] 9 7 0 0 [2,] 7 9 7 0 [3,] 0 7 9 7 [4,] 0 0 7 9 > det(aa) [1] -2945 Leonid -------------------------------------- Leonid Gibiansky, Ph.D. President, QuantPharm LLC web: www.quantpharm.com e-mail: LGibiansky at quantpharm.com tel: (301) 767 5566 Sam Liao wrote: > Dear NONMEM users: > > Can someone please help me to solve this problem with a band matrix? > > $OMEGA BLOCK(4) > 0.09 ;BSV_V1C > 0.07 0.09 ;BSV_CLC > 0 0.07 0.09 ;BSV_CLN > 0 0 0.07 0.09 ;BSV_V1N > Why this one above is getting an error in NONMEM? > > $OMEGA BLOCK(4) > 0.09 ;BSV_V1C > 0.07 0.09 ;BSV_CLC > 0 0 0.09 ;BSV_CLN > 0 0 0.07 0.09 ;BSV_V1N > > This one above is fine, but I need to run a simulation in which there are some correlation between CLC and CLN. > > There were some very helpful discussion on band matrix few years ago. But I still couldn't figure out why this band matrix not permissible. > > Sam Liao > http://www.cognigencorp.com/nonmem/nm/96mar232001.html