This data are kilojoules of energy that are consumed in starving fish over a
time period (Days).  The KJ reach a lower asymptote and level off and I
would like to use a non-linear plot to show this leveling off.  The data are
noisy and the sample sizes not the largest.  I have tried selfstarting
weibull curves and tried the following, both end with errors.

Days<-c(12, 12, 12, 12, 22, 22, 22, 22, 32, 32, 32, 32, 37, 38, 38, 39, 39,
39, 39, 39, 39, 39,  1,  1,  1,  1)
Joules<-c(8.782010,  8.540524,  8.507526, 11.296904,  4.232690, 13.026588,
10.213342,  4.771482,  4.560359,  6.146684, 9.651727,  8.064329,  9.419335,
7.129264,  6.079012,  7.095888, 17.996794,  7.028287,  8.028352,  5.497564,
11.607090,  9.987215, 11.065307, 21.433094, 20.366385, 22.475717)
X11()
par(cex=1.6)
plot(Joules~Days,xlab="Days after fasting was initiated",ylab="Mean energy
per fish (KJ)")
model<-nls(joules~a+b*exp(-c*Days),start=list(a=8,b=9,c=-.229),
control=list(minFactor=1e-12),trace=TRUE)
summary(model)

init <- nls(Joules~ SSweibull(Days,Asym,Drop,lrc,pwr),
control=list(minFactor=1e-12),data=.GlobalEnv)
init
Data here is reproducible.

As always, thank you...keith

-- 
M. Keith Cox, Ph.D.
Alaska NOAA Fisheries, National Marine Fisheries Service
Auke Bay Laboratories
17109 Pt. Lena Loop Rd.
Juneau, AK 99801
Keith.Cox@noaa.gov
marlinkcox@gmail.com
U.S. (907) 789-6603

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