T matrix

From:"Emily" Subject:[NMusers] T matrix Date:Fri, March 8, 2002 9:39 am Dear nmusers: First, I'd like to thank Nick. After gave smaller Vm and bigger k12, I still got the same error message. What esle can I do ? See 99mar072002.html for previous related discussion. And I'd like to ask a few questions: Regarding the questions of T-matrix as well as R and S matrixes, I am still confused by the following questions. I hope you can give me some inputs: (1). When a T matrix is in output, does this mean either R matrix or S matrix is sigular (but not both)? (2) Does minimization appears only if R matrix is not singular (no matter what S matrix is)? (3). How a T matrix could be used to estimate the confidence region of parameters? (4) As you can see in my previous message, my control file indicates that over-parameterization may not exist. If so, then why I still get a message of R matrix algorithmically singular? By the way, in nonmem user guide part VIII, page 114, it mentioned that, for nonlinear model, ADVAN8 may be a preference to ADVAN6 when the differential equations are stiff. What does the stiff mean here? Thaks a lot !!