# SSexpoGrowth: Exponential growth function In OnofriAndreaPG/aomisc: Statistical methods for the agricultural sciences

 expoGrowth R Documentation

## Exponential growth function

### Description

These functions provide the exponential growth function (expoGrowth), the exponential growth function with self-starter for the nls function and the exponential growth function with self-starter for the drm function in the drc package.

### Usage

  expoGrowth.fun(predictor, init, k)
NLS.expoGrowth(predictor, init, k)
DRC.expoGrowth(fixed = c(NA, NA), names = c("init", "k"), ...)


### Arguments

 fixed numeric vector. Specifies which parameters are fixed and at what value they are fixed. NAs for parameter that are not fixed. names a vector of character strings giving the names of the parameters. The default is reasonable.

### Details

The exponential growth is given by the following function:

f(x) = \textrm{init} \cdot \exp (k x )\}

### Value

expoGrowth.fun and NLS.expoGrowth return a numeric value, while DRC.expoGrowth returns a list containing the nonlinear function, the self starter function and the parameter names.

### Note

DRC.expoGrowth is for use with the function drm.

Andrea Onofri

### References

Ratkowsky, DA (1990) Handbook of nonlinear regression models. New York (USA): Marcel Dekker Inc.

Onofri, A. (2020). A collection of self-starters for nonlinear regression in R. See: https://www.statforbiology.com/2020/stat_nls_usefulfunctions/

### Examples

rm(list=ls())
set.seed(1234)
X <- 1:20
Ye <- 3 * exp(0.1 * X)
Y <- Ye + rnorm(20, 0, 0.7)
dataset <- data.frame(X, Y)
rm(X, Y)

model <- drm(Y ~ X, fct = DRC.expoGrowth(),
data = dataset)
model2 <- nls(Y ~ NLS.expoGrowth(X, a, b),
data = dataset)
summary(model)
summary(model2)


OnofriAndreaPG/aomisc documentation built on Feb. 2, 2023, 12:13 p.m.