Transform an lm or glm model into a function

Transform an lm or glm model that has only two variables into a function (useful for plotting, see examples).

Usage

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

Arguments

x: An lm or glm 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("trees", package = "datasets")
trees_lm1 <- lm(Volume ~ Girth, data = trees)
trees_lm2 <- lm(Volume ~ Girth + I(Girth^2), data = trees)

# Compare these two models on a chart
library(chart)
#> Loading required package: ggplot2
#> Loading required package: lattice
chart(trees, Volume ~ Girth) +
  geom_point() +
  stat_function(fun = as.function(trees_lm1), col = "red") +
  stat_function(fun = as.function(trees_lm2), col = "blue")


# The created function can also be used for easy predictions
trees_fn1 <- as.function(trees_lm1)
trees_fn1(10:20) # Volume for Girth 10:20
#>        1        2        3        4        5        6        7        8 
#> 13.71511 18.78096 23.84682 28.91267 33.97853 39.04439 44.11024 49.17610 
#>        9       10       11 
#> 54.24196 59.30781 64.37367