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.

Usage

CO2

Format

An object of class c("nfnGroupedData", "nfGroupedData", "groupedData", "data.frame") containing 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 (\mu\mbox{mol}/m^2 sec).

Details

The CO_2 uptake of six plants from Quebec and six plants from Mississippi was measured at several levels of ambient CO_2 concentration. Half the plants of each type were chilled overnight before the experiment was conducted.

This dataset was originally part of package nlme, and that has methods (including for [, as.data.frame, plot and print) for its grouped-data classes.

Source

⁠Potvin, Lechowicz, and Tardif (1990); ⁠Pinheiro and Bates (2000)

References

⁠Pinheiro J, Bates DM (2000). Mixed-Effects Models in S and S-PLUS, series Statistics and Computing. Springer New York. ISBN 9780387989570.

⁠Potvin C, Lechowicz MJ, Tardif S (1990). “The Statistical Analysis of Ecophysiological Response Curves Obtained from Experiments Involving Repeated Measures.” Ecology, 71(4), 1389–1400. doi:10.2307/1938276.

Examples

require(stats); require(graphics)

coplot(uptake ~ conc | Plant, data = CO2, show.given = 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
print(sapply(fmlist, coef), digits = 3)