Dear NMusers,
Our NONMEM User Guides are full of good advice and they are searchable. Yet
when I tried to find out whether any of the estimation methods could be
enticed to give me the inverse Wishart matrix needed to specify PRIORS for
OMEGAs, I found no help. Leonid G. mentions the inverse Wis
Joachim,
Please see the CRAN package "metrumrg". Look for the function
"riwish", written by Leonid Gibiansky. Any errors are mine
(maintainer).
-Tim
Tim Bergsma, PhD
Metrum Research Group LLC
Tariffville, CT
860-930-9931
On Wed, Feb 22, 2012 at 7:53 AM, Joachim Grevel wrote:
> Dear NMusers,
Dear Coen,
There I do have the answer: with MCMC Bayesian in NONMEM 7.1 you have to use
NWPRI according to the guide.
Dear Nidal,
What I try to do is that: use an existing very well defined popPK model
(2500 conc in 200 patients) to obtain individual PK parameters in only 20
additional
Dear Joachim,
The IW distribution is not something you get from NONMEM, you have to give
the degrees of freedom of the IW prior distribution. Normally this is at or
below the number of subjects in you previous study depending the information
about the parameter per subject.
In addition to U
Joachim,
I found the following also useful in calculating df from IW distribution.
Dansirikul C, Morris RG, Tett SE, Duffull SB.
A Bayesian approach for population pharmacokinetic modelling of sirolimus. Br J
Clin Pharmacol. 2006 Oct;62(4):420-34.
Regards,
Ayyappa
From: owner-nmus...@globoma
Hi
An appropriate value for dof of the IW is difficult to determine. While it can
be set at n-1 from a prior this is somewhat arbitrary. It is not in this sense
like a t-distn where we calculate dof in this manner.
You would have to get a feeling for the degree of spread in your deviates give
Hi again,
We use a formula to come up with a suitable number of subjects (N) for
degrees of freedom (df) for IW distribution. It is based on the assumption
that you know the SE of the variance estimate that you want to use as a
prior.
. How to choose N?
. We know 0 < N <
