CO2 {nls} | R Documentation

## Carbon Dioxide uptake in grass plants

### Description

The `CO2` data frame has 84 rows and 5 columns of data from an experiment on the cold tolerance of the grass species Echinochloa crus-galli

### Format

This data frame contains the following columns:

Plant
  an ordered factor with levels `Qn1` < `Qn2` < `Qn3` < ...{} < `Mc1` giving a unique identifier for each plant.
Type
  a factor with levels `Quebec` `Mississippi` giving the origin of the plant
Treatment
  a factor with levels `nonchilled` `chilled`
conc
  a numeric vector of ambient carbon dioxide concentrations (mL/L).
uptake
  a numeric vector of carbon dioxide uptake rates (umol/m^2 sec).

### Details

The CO2 uptake of six plants from Quebec and six plants from Mississippi was measured at several levels of ambient CO2 concentration. Half the plants of each type were chilled overnight before the experiment was conducted.

### Source

Potvin, C., Lechowicz, M. J. and Tardif, S. (1990) ``The statistical analysis of ecophysiological response curves obtained from experiments involving repeated measures'', Ecology, 71, 1389–1400.

Pinheiro, J. C. and Bates, D. M. (2000) Mixed-effects Models in S and S-PLUS, Springer.

### Examples

    library(nls)
    data(CO2)
    coplot(uptake ~ conc | Plant, data = CO2, show = FALSE, type = "b")
    ## fit the data for the first plant
    fm1 <- nls(uptake ~ SSasymp(conc, Asym, lrc, c0),
       data = CO2, subset = Plant == 'Qn1')
    summary(fm1)
    ## fit each plant separately
    fmlist <- list()
    for (pp in levels(CO2$Plant)) {
      fmlist[[pp]] <- nls(uptake ~ SSasymp(conc, Asym, lrc, c0),
          data = CO2, subset = Plant == pp)
    }
    ## check the coefficients by plant
    sapply(fmlist, coef)

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