abline {graphics}R Documentation

Add a Straight Line to a Plot


This function adds one or more straight lines through the current plot.


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


a, b the intercept and slope, single values.
untf logical asking whether to untransform. See Details.
h the y-value(s) for horizontal line(s).
v the x-value(s) for vertical line(s).
coef a vector of length two giving the intercept and slope.
reg an object with a coef component. See Details.
... graphical parameters such as col, lty and lwd (possibly as vectors: see Details).


The first form 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 intercept and slope.

If untf is true, and one or both axes are log-transformed, then a curve is drawn corresponding to a line in original coordinates, otherwise a line is drawn in the transformed coordinate system. The h and v parameters always refer to original coordinates.

The graphical parameters col, lty and lwd can be specified; see par for details. For the h= and v= cases they can be vectors of length greater than one, recycled as necessary.


Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.

See Also

lines and segments for connected and arbitrary lines given by their endpoints. par.


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

[Package graphics version 2.2.1 Index]