SSpexpf: self start for plateau-exponential function

In nlraa: Nonlinear Regression for Agricultural Applications

self start for plateau-exponential function

Description

Self starter for an plateau-exponential function

Usage

pexpf(x, a, xs, c)

SSpexpf(x, a, xs, c)

Arguments

x	input vector (x)
a	represents the value for the plateau
xs	represents the breakpoint at which the plateau ends
c	represents the exponential rate

Details

The equation is: for x < xs: y = a and x >= xs: a * exp(c * (x-xs)).

Value

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

pexpf: vector of the same length as x using the pexpf function

Examples

require(ggplot2)
set.seed(1234)
x <- 1:30
y <- pexpf(x, 20, 15, -0.2) + rnorm(30, 0, 1)
dat <- data.frame(x = x, y = y)
fit <- nls(y ~ SSpexpf(x, a, xs, c), data = dat)
## plot
ggplot(data = dat, aes(x = x, y = y)) + 
  geom_point() + 
  geom_line(aes(y = fitted(fit)))

nlraa documentation built on Aug. 21, 2025, 5:59 p.m.