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)
Arguments
nx, ny
number of cells of the grid in x and y direction. When
NULL, as per default, the grid aligns with the tick marks on
the corresponding default axis (i.e., tickmarks as computed by
axTicks ). When NA , no grid lines are
drawn in the corresponding direction.
col
character or (integer) numeric; color of the grid lines.
lty
character or (integer) numeric; line type of the grid lines.
lwd
non-negative 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 equilogs =
FALSE in that case gives non equidistant tick aligned
grid lines.
Note
If more fine tuning is required, use abline(h = ., v = .)
directly.
References
Murrell, P. (2005) R Graphics. Chapman & Hall/CRC Press.
See Also
plot , abline , lines ,
points .
Examples
plot(1:3)
grid(NA, 5, lwd = 2) # grid only in y-direction
## 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 log-scale 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))))