grid {graphics}  R Documentation 
Add Grid to a Plot
Description
grid
adds an nx
by ny
rectangular grid to an
existing plot.
Usage
grid(nx = NULL, ny = nx, col = "lightgray", lty = "dotted",
lwd = par("lwd"), equilogs = TRUE, nintLog = NULL)
Arguments
nx , ny 
number of cells of the grid in x and y direction. When

col 
character or (integer) numeric; color of the grid lines. 
lty 
character or (integer) numeric; line type of the grid lines. 
lwd 
nonnegative numeric giving line width of the grid lines. 
equilogs 
logical, only used when log coordinates and
alignment with the axis tick marks are active. Setting 
<<<<<<< .mine
nintLog 
one or two integers (or 
 .r86704 =======
nintLog 
one or two integers (or 
>>>>>>> .r86709
Value
A list of the x ("atx"
) and y ("aty"
) coordinates at
which the grid lines were drawn is returned invisibly.
Note
If more fine tuning is required, use abline(h = ., v = .)
directly.
References
Murrell, P. (2005) R Graphics. Chapman & Hall/CRC Press.
See Also
Examples
plot(1:3)
grid(NA, 5, lwd = 2) # grid only in ydirection
## maybe change the desired number of tick marks: par(lab = c(mx, my, 7))
op < par(mfcol = 1:2)
with(iris,
{
plot(Sepal.Length, Sepal.Width, col = as.integer(Species),
xlim = c(4, 8), ylim = c(2, 4.5), panel.first = grid(),
main = "with(iris, plot(...., panel.first = grid(), ..) )")
plot(Sepal.Length, Sepal.Width, col = as.integer(Species),
panel.first = grid(3, lty = 1, lwd = 2),
main = "... panel.first = grid(3, lty = 1, lwd = 2), ..")
}
)
par(op)
plot(1:64)
gr < grid() # now *invisibly* returns the grid "at" locations
str(gr)
stopifnot(length(gr) == 2, identical(gr[[1]], gr[[2]]),
gr[["atx"]] == 10*(0:6))
## In logscale plots :
plot(8:270, log="xy") ; grid() # at (1, 10, 100); if preferring "all" grid lines:
plot(8:270, log="xy") ; grid(equilogs = FALSE) > grll
stopifnot(identical(grll, list(atx = c(1, 2, 5, 10, 20, 50, 100, 200),
aty = c( 10, 20, 50, 100, 200))))
x < 2^(9:70)
plot(log(x) ~ x, log="xy")
grll < grid(equilogs = FALSE, col = adjustcolor("green", 1/3))
gr20 < grid(nintLog = 20)
gr25 < grid(nintLog = 25, col="thistle")
str(gr25)
stopifnot(exprs = {
grll$aty == c(1, 2, 5, 10, 20, 50)
length(gr20$atx) >= 20 # 24 effectively
all.equal(10^(3:22), gr25$atx, tol = 1e15) # even tol = 0
})