BOD {nls} | R Documentation

## Biochemical Oxygen Demand

### Description

The `BOD` data frame has 6 rows and 2 columns giving the biochemical oxygen demand versus time in an evaluation of water quality.

### Format

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).

### Source

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.

### Examples

    library(nls)
    data(BOD)
    # 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)
    print(fm1)
    # using the plinear algorithm
    fm2 <- nls(demand ~ (1-exp(-exp(lrc)*Time)), data = BOD,
       start = c(lrc = log(.35)), algorithm = "plinear", trace = TRUE)
    # using a self-starting model
    fm3 <- nls(demand ~ SSasympOrig(Time, A, lrc), data = BOD)
    summary( fm3 )

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