NONMEM Users Network Archive

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algorithm limits

From: Mark Sale - Next Level Solutions <mark>
Date: Sat, 19 Jul 2008 13:13:09 -0700
<= /tr>
General question:
  What are practical limits on the magnitude o= f OMEGA that is compatible with the FO and FOCE/I method?  I seem to r= ecall Stuart at one time suggesting that a CV of 0.5 (exponential OMEGA of = 0.5) was about the limit at which the Taylor expansion can be considered a = reasonable approximation of the real distribution. What about FOCE-I?
&n= bsp;I'm asking because I have a model that has an OMEGA of 13, exponential = (and sometime 100) FOCE-I, and it seems to be very poorly behaved in spite = of overall, reasoable looking data (i.e., the structural model traces a lin= e that looks like the data, but some people are WAY above the line and some= are WAY below, and some rise MUCH faster, and some rise MUCH later, by way= I mean >10,000 fold, but residual error looks not too bad).  Looki= ng at the raw data, I believe that the the variability is at least this lar= ge.  Can I beleive that NONMEM FOCE (FO?) will behave reasonably?
t= hanks
Mark



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Received on Sat Jul 19 2008 - 16:13:09 EDT

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