CO2                   package: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:

     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)

