abline {graphics} | 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, ...)
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 asking to *untransform*. 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 always refer to original coordinates.

The graphical parameters `col`

and `lty`

can be specified as
arguments to `abline`

; see `par`

for details.

### References

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`

.

### Examples

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

[Package

*graphics* version 2.1.0

Index]