CO2

Attachment Size
dataset-23612.csv 3.14 KB
Description

Carbon Dioxide Uptake in Grass Plants

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
(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.

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, 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

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)