Re: [R] Proper syntax for using varConstPower in nlme

2009-10-18 Thread Kingsford Jones
On Fri, Oct 16, 2009 at 3:56 PM, Michael A. Gilchrist mi...@utk.edu wrote: Hi Dieter, Thanks for the reply.  I had played with the initial conditions, but apparently not enough.  I finally found some that avoided the singularity issue.  Many thanks. More generally, I went over the

Re: [R] Proper syntax for using varConstPower in nlme

2009-10-16 Thread Dieter Menne
Michael A. Gilchrist wrote: - nlme(Count ~ quad.PBMC.model(aL, aN, T0), + data = tissueData, + weights = varConstPower(form =~ Count), + start = list( fixed = c(rep(1000, 8), -2, -2) ), + fixed = list(T0 ~ TypeTissue-1, aL ~ 1, aN ~

Re: [R] Proper syntax for using varConstPower in nlme

2009-10-16 Thread Michael A. Gilchrist
Hi Dieter, Thanks for the reply. I had played with the initial conditions, but apparently not enough. I finally found some that avoided the singularity issue. Many thanks. More generally, I went over the documentation yet again in PB and I still find it a bit confusing. They talk about

[R] Proper syntax for using varConstPower in nlme

2009-10-15 Thread Michael A. Gilchrist
Hello, Excuse me for posting two questions in one day, but I figured it would be better to ask my questions in separate emails. I will again give the caveat that I'm not a statistician by training, but have a fairly decent understanding of probability and likelihood. As before, I'm trying