| abline {graphics} | R Documentation |
Add Straight Lines to a Plot
Description
This function adds one or more straight lines through the current plot.
Usage
abline(a = NULL, b = NULL, h = NULL, v = NULL, reg = NULL,
coef = NULL, untf = FALSE, ...)
Arguments
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 |
... |
graphical parameters such as
|
Details
Typical usages are
abline(a, b, ...) abline(h =, ...) abline(v =, ...) abline(coef =, ...) abline(reg =, ...)
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.
Specifying an xpd argument for clipping overrides
the global par("xpd") setting used otherwise.
References
Becker RA, Chambers JM, Wilks AR (1988). The New S Language. Chapman and Hall/CRC, London.
Murrell P (2005). R Graphics, series Chapman & Hall/CRC The R Series. CRC Press. ISBN 9781420035025.
See Also
lines and segments for connected and
arbitrary lines given by their endpoints.
par.
Examples
## 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:
require(stats)
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")