
These models describe the response of germination rate to water potential in the substrate.
GRPsiLin()
GRPsiPol()
GRPsiPol2()
GRPsi.Lin()
GRPsi.Pol()
GRPsi.Pol2()
GRPsiLin.fun(Psi, Psib, thetaH)
GRPsiPol.fun(Psi, Psib, thetaH)
GRPsiPol2.fun(Psi, Psib, thetaH)
The 'GRPsiLin.fun()', 'GRPsiPol.fun()' and 'GRPsiPol2.fun()' functions return the germination rate for any given values of water potential in the substrate. The 'GRPsiLin()', 'GRPsiPol()' and 'GRPsiPol2()' (and 'GRPsi.Lin()', 'GRPsi.Pol()' and 'GRPsi.Pol2()') functions return a list containing the nonlinear function, the self starter function, the parameter names and other items which are internally used by the 'drc()' function.
The functions 'GRPsiLin()', 'GRPsiPol()', 'GRPsiPol2()', GRPsi.Lin(), GRPsi.Pol(), GRPsi.Pol2() have no arguments. The functions 'GRPsiLin.fun()', 'GRPsiPol.fun()' and 'GRPsiPol2.fun()' have the following arguments:
Water potential in the substrate
Base water potential within the population
Hydro-time parameter
Andrea Onofri
The functions 'GRPsiLin()', 'GRPsiPol()', 'GRPsiPol2()', GRPsi.Lin(), GRPsi.Pol(), GRPsi.Pol2() are meant to be used with the 'drm()' function in the 'drc' package ('GRPsiLin()' and 'GRPsi.Lin()', 'GRPsiPol()' and 'GRPsi.Pol()', 'GRPsiPol2()' and 'GRPsiPol2()' are totally equivalent, apart from the names). The functions 'GRPsiLin.fun()', 'GRPsiPol.fun()' and 'GRPsiPol2.fun()' are used for general purposes (plotting and other uses). Details about these functions and the meaning of parameters are described in Bradford (2002) and in the package ducumentation (see references below).
See package documentation at: https://www.statforbiology.com/_seedtutorial/
library(drcte)
# Observed data
Psi <- c(-2, -1.5, -1.2, -1, -0.8, -0.6, -0.4, -0.25,
-0.12, -0.06, -0.03, 0)
GR <- c(0, 0, 0, 0, 0.0585, 0.094, 0.1231, 0.1351,
0.1418, 0.1453, 0.1458, 0.1459)
Psi2 <- c(-0.5, -0.6, -0.7, -0.8, -0.9, -1, -1.1, -1.2,
-1.5)
GR2 <- c(1.4018, 1.0071, 0.5614, 0.3546, 0.2293, 0, 0,
0, 0)
# Model fitting
modHT1 <- drm(GR ~ Psi, fct = GRPsiLin())
modHT2 <- drm(GR ~ Psi, fct = GRPsiPol())
modHT3 <- drm(GR2 ~ Psi2, fct = GRPsiPol2())
summary(modHT1)
summary(modHT2)
summary(modHT2)
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