.BG
.VE $Header: /usr3/s/current/s/.help/RCS/abline,v 1.2 83/12/30 19:22:40 rab Exp $
.FN abline
.TL
abline: Plot Line in Intercept-Slope form
.CS
abline(a, b)
abline(reg)
abline(coef)

abline(h=)
abline(v=)
.PP
.AG reg
a regression structure; i.e., `reg' is a structure that
contains a component `coef' giving coefficients of a fitted
line (with intercept term first).
If the `coef' component contains a single number, it is treated as
the slope of a fit through the origin.
.AG coef
vector containing the intercept `a' and slope `b' of the
line y=`a'+`b'*x.
.AG a,b
intercept and slope as above.
.AG h
vector of y-coordinates for horizontal lines across plot.
.AG v
vector of x-coordinates for vertical lines across plot.
.PP
Graphical parameters may also be supplied as arguments to this
function (see `par').
.PP
The effect of `abline' is that the line y=`a'+`b'*x
or the specified horizontal and vertical lines are drawn across the
current plot.
A warning is given if an intercept/slope line does not intersect the plot.
.EX
abline(0,1)     #draws line with 0 intercept and slope 1
abline(reg(x,y))     #line produced by least-squares fit to x and y
abline(v=c(0,10),lty=2)     # dotted vertical lines at x==0 and 10
.KW plot*
.KW aplot*
.WR
