SSexplin: self start for the exponential-linear growth equation

In nlraa: Nonlinear Regression for Agricultural Applications

self start for the exponential-linear growth equation

Description

Self starter for an exponential-linear growth equation

Usage

explin(t, cm, rm, tb)

SSexplin(t, cm, rm, tb)

Arguments

t	input vector (time)
cm	parameter related to the maximum growth during the linear phase
rm	parameter related to the maximum growth during the exponential phase
tb	time at which switch happens

Details

J. GOUDRIAAN, J. L. MONTEITH, A Mathematical Function for Crop Growth Based on Light Interception and Leaf Area Expansion, Annals of Botany, Volume 66, Issue 6, December 1990, Pages 695–701, \Sexpr[results=rd]{tools:::Rd_expr_doi("10.1093/oxfordjournals.aob.a088084")}

The equation is:

(cm/rm) * log(1 + exp(rm * (t - tb)))

This function is described in Archontoulis and Miguez (2015) - (doi:10.2134/agronj2012.0506).

Value

a numeric vector of the same length as x containing parameter estimates for equation specified

explin: vector of the same length as x using a explin function

Examples

require(ggplot2)
set.seed(12345)
x <- seq(1,100, by = 5)
y <- explin(x, 20, 0.14, 30) + rnorm(length(x), 0, 5)
y <- abs(y)
dat <- data.frame(x = x, y = y)
fit <- nls(y ~ SSexplin(x, cm, rm, tb), data = dat)
## plot
ggplot(data = dat, aes(x = x, y = y)) + 
  geom_point() + 
  geom_line(aes(y = fitted(fit)))

nlraa documentation built on May 29, 2024, 2:01 a.m.