Description Format Source Examples
The Leaves
data frame has 15 rows and 2 columns of leaf length
over time.
This data frame contains the following columns:
time from initial emergence (days).
leaf length (cm).
Bates and Watts (1998), Nonlinear Regression Analysis and Its Applications, Wiley (Appendix A4.5).
Originally from Heyes and Brown (1956) in F.L. Milthorpe (ed), The Growth of Leaves, London: Butterworth.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19  options(show.signif.stars = FALSE)
## first fit a logistic model
fm1 < nls(Length ~ SSlogis(Time, Asym, xmid, scal), data = Leaves)
summary(fm1)
plotfit(fm1, xlab = "Time from initial emergence (days)",
ylab = "Leaf length (cm)", main = "Logistic growth model")
## compare with Richards growth model
fm2 < nls(Length ~ Asym/(1+exp((Time  xmid)/scal))^exp(lpow), Leaves,
c(coef(fm1),c(lpow = 0)))
summary(fm2)
anova(fm1, fm2)
plotfit(fm2, xlab = "Time from initial emergence (days)",
ylab = "Leaf length (cm)", main = "Richards growth model")
pm1 < profile(fm1)
plot(pm1, aspect = 'xy', layout = c(3,1))
plot(pm1, absVal = FALSE, aspect = 'xy', layout = c(3,1))
pm2 < profile(fm2, alpha = 0.05)
plot(pm2, aspect = 'xy', layout = c(4,1))
plot(pm2, absVal = FALSE, aspect = 'xy', layout = c(4,1))

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