RE: How to model observed quantity tha is an average over compartments
Hi Dieter,
If you only onserve the average of two quantities you can never estimate the
individual contributions.
You must have some additional information to be able to do this.
Maybe if the time constants are apriori known to be very different, i.e. fast
and slow, then it might be
possible but you would need very rich data. Multiple fast and slow changes in
concentration.
As far as $ERROR is concerned it is quite easy to setup when you use A()
$ERROR
....
CT1=A(1)/V1 ;conc in tissue 1
CT2=A(2)/V2 ;conc in tissue 2
COBS=(CT1+CT2)/2 ;average in tissues
Y=COBS*(1+ERR(1)) ;Just guessing proportional error
...
Hope this helps,
Doug Eleveld
Quoted reply history
-----Original Message-----
From: [email protected] on behalf of Dieter Menne
Sent: Thu 7/29/2010 5:49 PM
To: [email protected]
Subject: [NMusers] How to model observed quantity tha is an average over
compartments
Dear Nmusers,
we have rich concentration data from tissues measured with MRI techniques.
From other results, we know that the following model is a good
approximation of biology
|
C <> T1 <> T2
|
However, we cannot observe T1 and T2 directly, since these are mixed on
cellular level and our resolution in mm-range.
We only see the tissue-average of T1 and T2.
I assume that I have to tweak $ERROR to model the averaging. Could someone
point me to a similar example? I could not find an example on the list that
has a CMT in $ERROR.
Dieter Menne