Gompertz equation (Gompertz, 1825)

Description

Gompertz equation (Gompertz, 1825). This is equation 2.3 in Table 1.

Usage

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gompertz(time, tmax, theta, Yo)

Arguments

time

a numeric vector of values at which to evaluate the model.

tmax

tmax is the time when crop growth rate is maximum and Y = Yo/exp

theta

theta determines the curvature

Yo

Yo is the max Y

Details

An alternative way to Richards equation to generate asymetric growth with less parameters Applied to describe water stress index, crop N-uptake, seed germination, crop growth, LAI development, etc. Remark at time = 0, Y is not zero

Value

a numeric vector of length equal to the inputs

Author(s)

Fernando E. Miguez

References

Nonlinear Regression Models and Applications in Agricultural Research. Sotirios V. Archontoulis and Fernando E. Miguez. Agronomy Journal. doi: 10.2134/agronj2012.0506

See Also

SSgompertz

Examples

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require(lattice)
## Set parameter values and plot the relationship
time <- seq(0, 150,5)
ans1 <- gompertz(time, tmax = 60, theta = 0.09, Yo=100)
ans2 <- gompertz(time, tmax = 60, theta = 0.07, Yo=100)
ans3 <- gompertz(time, tmax = 60, theta = 0.05, Yo=100)
ans4 <- gompertz(time, tmax = 60, theta = 0.03, Yo=100)
xyplot(ans1 + ans2 + ans3 + ans4 ~ time, type="l", auto.key=TRUE, ylab = "text", xlab = "time")