search for: solb1wvb

Displaying 1 result from an estimated 1 matches for "solb1wvb".

2005 Jan 27
3
weighting in nls
...so I'm weighting by n/ variance, where the variance is well known from a large data set. This weighting factor is available as the variable 'novervar'. The function is a von Bertalanffy curve of the form weight~(a*(1-exp(-b*(age-c))))^3. Thus I'm entering the command in the form: solb1wvb<-nls(~sqrt(novervar)*(weight-(a*(1-exp(-b*(age-c))))^3),data=solb1.na.rm,start=list(a=0.85,b=0.45,c=0.48)) Can anyone suggest what I'm doing wrong? I seem to be folowing the instructions in MASS. I tried following the similar instructions on page 450 of the white book but these were a bit...