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Add a Straight Line to a Plot

Syntax

abline(a, b, ...)
abline(h=, ...)
abline(v=, ...)
abline(coef=, ...)
abline(reg=, ...)

Value

This function is invoked for its side effects, which is to add one or more straight lines through the current plot. The first form above specifies the line in intercept/slope form (alternatively a can be specified on its own and is taken to contain the slope and intercept in vector form). The h= and v= forms draw horizontal and vertical lines at the specified coordinates. The coef form specifies the line by a vector containing the slope and intercept. reg is a regression object which contains reg$coef. If it is of length 1 then the value is taken to be the slope of a line through the origin, otherwise, the first 2 values are taken to be the slope and intercept.

The graphical parameters col and lty can be specified as arguments to abline; see par for details.

Examples

data(cars) z <- lm(dist ~ speed, data=cars) plot(cars) abline(z)