BOD data frame has 6 rows and 2 columns giving the
biochemical oxygen demand versus time in an evaluation of water
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, 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.
require(stats) # simplest form of fitting a first-order model to these data fm1 <- nls(demand ~ A*(1-exp(-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 ~ (1-exp(-exp(lrc)*Time)), data = BOD, start = c(lrc = log(.35)), algorithm = "plinear", trace = TRUE) ## IGNORE_RDIFF_END # using a self-starting model fm3 <- nls(demand ~ SSasympOrig(Time, A, lrc), data = BOD) summary(fm3)
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