one thing that you could do is multiply all the values by 1000 (i.e., change the units)
Dennis Fisher MD P < (The "P Less Than" Company) Phone / Fax: 1-866-PLessThan (1-866-753-7784) www.PLessThan.com <http://www.plessthan.com/> > On Jul 27, 2016, at 11:11 AM, Bharadwaj, Manushree > <manu...@ostatemail.okstate.edu> wrote: > > Dear friends, > > I log transformed the plasma concentrations in my data and I am using this > log transformed data as my dependent variable (DV). I imputed the BQLs to > LLOQ/2, which is my case is (1/2=0.5). The natural log of 0.5 is negative > which mean that I have negative values in my DV column. > While the parameter estimates look somewhat reliable, I have negative points > plotted in the diagnostic plots such as DV vs PRED, DV and PRED vs TIME, etc. > My questions are- > 1. What is the best way of dealing with <1 DV/plasma concentration values > while transforming into natural logarithm? > 2. In my situation discussed above, where I have negative DV values in my > data, has the NONMEM ignored or considered the negative numbers when > estimating the parameter values? > > Thank you, > Manu > > -- > With regards- > Manushree Bharadwaj, BVSc, PhD Candidate > Graduate Teaching Associate > Department of Physiological Sciences > Center for Veterinary Health Sciences > Oklahoma State University > Stillwater, OK-74074
