abline {graphics} | R Documentation |

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

abline(a = NULL, b = NULL, h = NULL, v = NULL, reg = NULL, coef = NULL, 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` method. See Details. |

`...` |
graphical parameters such as
`col` , `lty` and `lwd` (possibly as vectors: see
Details) and the line characteristics `lend` , `ljoin` and
`lmitre` . |

Typical usages are

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

method.
If this returns a vector 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=`

usages 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.

Murrell, P. (2005) *R Graphics*. Chapman & Hall/CRC Press.

`lines`

and `segments`

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

.

## Setup up coordinate system (with x==y aspect ratio): plot(c(-2,3), c(-1,5), type = "n", xlab="x", ylab="y", asp = 1) ## the x- and y-axis, and an integer grid abline(h=0, v=0, col = "gray60") text(1,0, "abline( h = 0 )", col = "gray60", adj = c(0, -.1)) abline(h = -1:5, v = -2:3, col = "lightgray", lty=3) abline(a=1, b=2, col = 2) text(1,3, "abline( 1, 2 )", col=2, adj=c(-.1,-.1)) ## Simple Regression Lines: sale5 <- c(6, 4, 9, 7, 6, 12, 8, 10, 9, 13) plot(sale5) abline(lsfit(1:10,sale5)) abline(lsfit(1:10,sale5, intercept = FALSE), col= 4) # less fitting z <- lm(dist ~ speed, data = cars) plot(cars) abline(z) # equivalent to abline(reg = z) or abline(coef = coef(z)) ## trivial intercept model abline(mC <- lm(dist ~ 1, data = cars)) ## the same as abline(a = coef(mC), b = 0, col = "blue")

[Package *graphics* version 2.5.0 Index]