SSexplin: self start for the exponential-linear growth equation
In femiguez/nlraa: Nonlinear Regression for Agricultural Applications

SSexplin

R Documentation

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)))

femiguez/nlraa documentation built on Jan. 26, 2024, 9:31 p.m.