Transform an nls model into a function

Transforming an nls model into a function could be useful to plot or otherwise manipulate it, see examples.

Usage

# S3 method for nls
as.function(x, ...)

Arguments

x

An nls model

...

Further arguments to the method (not used for now)

Value

A function with argument x that returns the values predicted by the model for these values of x.

Examples

data("ChickWeight", package = "datasets")
chick1 <- ChickWeight[ChickWeight$Chick == 1, ]

# Adjust a logistic curve
chick1_logis <- nls(weight ~ SSlogis(Time, Asym, xmid, scal), data = chick1)

# Show this on a ggplot
library(ggplot2)
p <- ggplot(chick1, aes(x = Time, y = weight)) +
  geom_point() +
  stat_function(fun = as.function(chick1_logis), col = "red")
p


# Visually compare with another model (four-parameter logistic):
chick1_fpl <- nls(weight ~ SSfpl(Time, A, B, xmid, scal), data = chick1)

p + stat_function(fun = as.function(chick1_fpl), col = "blue")