Add Lines to a Panel

USAGE:

panel.abline(coef, ...) 
panel.abline(a, b, ...) 
panel.abline(reg, ...) 
panel.abline(h=, v=, ...) 

ARGUMENTS:

coef
vector containing the intercept a and slope b of the line y= a + b *x.
a,b
intercept and slope as above.
reg
a regression object, such as returned by lsfit. Specifically, reg$coef, if it is of length 2, will be used to define the intercept and slope of the line. If reg$coef is of length 1, it is treated as the slope of a fit through the origin.
h
vector of y-coordinates for horizontal lines across plot.
v
vector of x-coordinates for vertical lines across plot.
...
graphical parameters may be specified to control the line(s). The trellis parameter add.line provides default values of the line width ( lwd ), line type ( lty ), and color ( col ) parameters.

SIDE EFFECTS:

The effect of panel.abline is that the line y= a + b *x or the specified horizontal and vertical lines are drawn across the current plot.

SEE ALSO:

The function is similar to but it does not issue a warning message if the line does not intersect the plot and it uses the Trellis rendering parameters.

EXAMPLES:

     # line with 0 intercept and slope 1 
panel.abline(0,1) 
     # line produced by least-squares fit 
panel.abline(lsfit(longley.x[,1],longley.y)) 
     # dotted vertical lines at x==0 and 10 
panel.abline(v=c(0,10),lty=2)