[NMusers] $Error with log-transf​ormation

2012-04-30 Thread siwei Dai
Hi, NM users: I am a new NONMEM user and wish to get help from NM experts. I have a data from rats with concentration measured in both plasma and cerebrospinal fluid . Compared to plasma concentration, the concentration in brain is relatively small (up to 30 times difference). Due to the big rang

[NMusers] Re: [NMusers] $Error with log-transf​ormation

2012-04-30 Thread siwei Dai
our rationale to use rat data for population analysis with 6 > etas? > > > On Mon, Apr 30, 2012 at 8:41 AM, siwei Dai wrote: > >> Hi, NM users: >> >> I am a new NONMEM user and wish to get help from NM experts. >> >> I have a data from rats with concentrat

[NMusers] Time after dose

2012-07-05 Thread siwei Dai
Hi, Everyone: I am having trouble with getting the correct output of TAD (time after dose) and hoping to get your suggestions. Here is a brief description of my dataset: drug was given multiple dosing every 12 hours. All the dosing events were recorded in the input file. Observations were taken r

[NMusers] Additive residual error

2013-02-11 Thread siwei Dai
Hi, NM users: I have a typical 2-compartment model that can describe my data quite well, except the final gradient for the additive residual error is '0'. I therefore fix the additive residual error to '0', but then NM would not run. I tried different initial estimations for other parameters but t

[NMusers] Objective Function

2013-08-06 Thread siwei Dai
Dear NM users: When I tried to use MCMC Bayes method in NM7.2, I sometimes run into the following error message: “OBJECTIVE FUNCTION IS INFINITE. PROBLEM ENDED” I used simulated data. While the simulated data from some iterations did not have this error, some did. Can anyone give me an idea w

Re: [NMusers] Objective Function

2013-08-06 Thread siwei Dai
time? > > If it does, this might happen if an observation occurs exactly at the > estimated value of lag time or mtime. > > Luann > > On 8/6/2013 1:45 PM, siwei Dai wrote: > > Dear NM users: > > > > When I tried to use MCMC Bayes method in NM7.2, I sometimes ru

[NMusers] In real life

2013-08-13 Thread siwei Dai
Dear NM users: I have questions about the principles. It is rather common that clinical PK data are 'bad': very sparse sampling and/or the sampling stopped too early. (I understand that you can never make a useful model with 'bad' data, but in the case that you have to make a model from them). I

[NMusers] Time-varing covariate

2013-08-23 Thread siwei Dai
Hi, Dear NMusers: I want to add a time-varing covariate in my model. For example, blood pressure or blood flow as covariates. But I am not sure how to do it. I see some earlier threads to discuss it but they all use complicated methods. I am wondering if there are any new way to do it in NM 7.2?

Re: [NMusers] Time-varing covariate

2013-08-23 Thread siwei Dai
why you > think it is complicated to use time varying covariates? > > Best wishes, > > Nick > > > On 23/08/2013 6:00 p.m., siwei Dai wrote: > >> Hi, Dear NMusers: >> I want to add a time-varing covariate in my model. For example, blood >> pressure or

Re: [NMusers] Time-varing covariate

2013-08-26 Thread siwei Dai
time varying covariates? > > Best wishes, > > Nick > > > On 23/08/2013 6:00 p.m., siwei Dai wrote: > >> Hi, Dear NMusers: >> I want to add a time-varing covariate in my model. For example, blood >> pressure or blood flow as covariates. But I am not sure

Re: [NMusers] Transit Absorption Model in NONMEM

2013-12-10 Thread siwei Dai
Hi, Nick: Have been enjoying learning from you. A follow up question: you mentioned in your last message that model misspecification can result in large negative simulated predictions. Can you be more specific on this issue? In which situation it would happen? Any type of model misspecification,

[NMusers] Negative DV values

2014-10-02 Thread siwei Dai
Dear NM users: I have a dataset where some of the concentrations are reported as negative values. I believe that the concentrations were calculated using a standard curve. My instinct is to impute all the negative values to zero, but worry that it will introduce bias. A 2nd thought is using the

Re: [NMusers] Negative DV values

2014-10-03 Thread siwei Dai
while > ago to show this ( > http://page-meeting.org/pdf_assets/2413-PAGE_2010_poster_LLOQ_v1.pdf), > but it should be intuitive too. > best regards, > Ron > > -- > Ron Keizer, PharmD PhD > Dept. of Bioengineering & Therapeutic Sc

[NMusers] Minimization Terminated in Bootstrapping

2014-10-29 Thread siwei Dai
Dear NM users: I have a data set where the absorption phase is highly variable. A complicated absorption model (the TRANSIT model) significantly improve the model fit (OFV drops over 250) compared to a 1st-order absorption model with lag time. The complicated final model converged and the covarian

Re: [NMusers] Minimization Terminated in Bootstrapping

2014-10-30 Thread siwei Dai
Astellas Way, 2N.184 > > Northbrook, Il 60062 > > phone: 224-205-5855 > > fax: 224-205-5914 > > email: peter.bon...@astellas.com > > > > > > *From:* owner-nmus...@globomaxnm.com [mailto:owner-nmus...@globomaxnm.com] > *On Behalf Of *siwei Dai > *S