R/regLine.R

In car: Companion to Applied Regression

# draw regression line from model to extremes of fit (J. Fox)

# last modified 2 October 2009 by J. Fox
# 2017-11-30: substitute carPalette() for palette(). J. Fox
# 2019-11-14: change class(x) == "y" to inherits(x, "y")
 
regLine <- function(mod, col=carPalette()[2], lwd=2, lty=1, ...){
	if(!is.null(class(mod$na.action)) && inherits(mod$na.action, "exclude"))
		class(mod$na.action) <-"omit"
	coef <- coefficients(mod)
	if (length(coef) != 2) stop("requires simple linear regression")
	x <- model.matrix(mod)[,2]
	y <- fitted.values(mod)
	min <- which.min(x)
	max <- which.max(x)
	lines(c(x[min], x[max]), c(y[min], y[max]), col=col, lty=lty, lwd=lwd, ...)
}