abline                 package:base                 R Documentation

Add a Straight Line to a Plot

Description:

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

Usage:

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

Arguments:

     a,b: the intercept and slope.

    untf: logical.  See Details.

       h: the y-value for a horizontal line.

       v: the x-value for a vertical line.

    coef: a vector of length two giving the intercept and slope.

     reg: an object with a `coef' component. See Details.

     ...: graphical parameters.

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 alway refer to original coordinates.

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

See Also:

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

Examples:

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

