Description Format Source Examples
The BOD2
data frame has 8 rows and 2 columns giving the
biochemical oxygen demand versus time in an evaluation of water
quality.
This data frame contains the following columns:
A numeric vector giving the time of the measurement (days).
A numeric vector giving the biochemical oxygen demand (mg/l).
Bates and Watts (1998), Nonlinear Regression Analysis and Its Applications, Wiley, (Appendix A4.1).
Originally from Marske (1967), M.Sc. Thesis, University of Wisconsin - Madison.
1 2 3 4 5 6 7 8 9 10 11 12 | str(BOD2)
# simplest form of fitting a first-order model to these data
(fm1 <- nls(demand ~ A*(1-exp(-exp(lrc)*Time)), data = BOD2,
start = c(A = 2.2, lrc = log(0.25))))
coef(fm1)
# using the plinear algorithm
(fm2 <- nls(demand ~ (1-exp(-exp(lrc)*Time)), data = BOD2,
start = c(lrc = log(0.25)), algorithm = "plinear", trace = TRUE))
# using a self-starting model
(fm3 <- nls(demand ~ SSasympOrig(Time, A, lrc), data = BOD2))
plotfit(fm3, xlab = "Time (days)",
ylab = "Biochemical Oxygen Demand")
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