The BOD
data frame has 6 rows and 2 columns giving the
biochemical oxygen demand versus time in an evaluation of water
quality.
1 
This data frame contains the following columns:
Time
A numeric vector giving the time of the measurement (days).
demand
A numeric vector giving the biochemical oxygen demand (mg/l).
Bates, D.M. and Watts, D.G. (1988), Nonlinear Regression Analysis and Its Applications, Wiley, Appendix A1.4.
Originally from Marske (1967), Biochemical Oxygen Demand Data Interpretation Using Sum of Squares Surface M.Sc. Thesis, University of Wisconsin – Madison.
1 2 3 4 5 6 7 8 9 10 11 12 13 14  require(stats)
# simplest form of fitting a firstorder model to these data
fm1 < nls(demand ~ A*(1exp(exp(lrc)*Time)), data = BOD,
start = c(A = 20, lrc = log(.35)))
coef(fm1)
fm1
# using the plinear algorithm (trace o/p differs by platform)
## IGNORE_RDIFF_BEGIN
fm2 < nls(demand ~ (1exp(exp(lrc)*Time)), data = BOD,
start = c(lrc = log(.35)), algorithm = "plinear", trace = TRUE)
## IGNORE_RDIFF_END
# using a selfstarting model
fm3 < nls(demand ~ SSasympOrig(Time, A, lrc), data = BOD)
summary(fm3)

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