RE: Hessian of posterior density is non positive definite during search

Hello Everyone Huge thanks to Peter, Jeroen, Leonid, Jonathan, Nick, Matt, Marc, Andreas, Kyun-Seop, Shelley and all, for taking the time to look at my problem and for offering me such detailed and helpful advice, much appreciated. Apologies for the delay in replying, teaching duties have kept me from my modelling over the last few days. I've not finished with the analysis yet but certainly the main problem seemed to lie with my use of ALAG as many of you suspected. Once I removed these parameters from the control stream, the model minimized successfully (the late BLQ points seemed to bias the model fit but that's a separate issue!). My next step is to try to implement the method with transit compartments instead of ALAG... Very many thanks - have a great weekend! Best wishes Ann _______________________________________________________________________ Ann Rigby-Jones PhD MRSC Research Fellow in Pharmacokinetics & Pharmacodynamics Peninsula College of Medicine & Dentistry, UK _______________________________________________________________________