Re: Coding a triple absorption model
SUM=1+ EXP(THETA(1)+ETA(1)) + EXP(THETA(2)+ETA(2))
F1=EXP(THETA(1)+ETA(1))/SUM
F2=EXP(THETA(2)+ETA(2))/SUM
F3=1/SUM
--------------------------------------
Leonid Gibiansky, Ph.D.
President, QuantPharm LLC
web: www.quantpharm.com
e-mail: LGibiansky at quantpharm.com
tel: (301) 767 5566
Samtani, Mahesh [PRDUS] wrote:
> Dear NMusers,
>
> I am using a dual absorption model as follows (The dose is split into 2 fractions and the splitting fraction, THETA(.), is an estimated parameter in the model):
>
> TPH = LOG(THETA(.)/(1-THETA(.)))
> TH = EXP(TPH+ETA(.))/(1+EXP(TPH+ETA(.)))
> F2 = TH
> F1 = 1-TH
>
> However, upon prolonged sampling we can observe a 3rd shallow phase. I would like to use a 3-depot absorption process with F1, F2 and F3=1-F1-F2. Both F1 and F2 need etas using some type of transformation such that neither one of them exceed 1 nor does their sum exceed 1. Can some one kindly provide the NONMEM code.
>
> Thanking you in advance,
> Mahesh