Display Contours
Usage
contour(x = seq(0, 1, len = nrow(z)), y = seq(0, 1, len = ncol(z)), z,
nlevels = 10, levels = pretty(range(z, finite = TRUE), nlevels),
labcex = 0,
xlim = range(x, finite = TRUE), ylim = range(y, finite = TRUE),
col = par("fg"), lty = par("lty"), add = FALSE, ...)
Arguments
x,y
|
locations of grid lines at which the values in z are
measured. These must be in ascending order. By default, equally
spaced values from 0 to 1 are used. If x is a list,
its components x$x and x$y are used for x
and y, respectively. If the list has component z this
is used for z.
|
z
|
a matrix containing the values to be plotted (NAs are
allowed). Note that x can be used instead of z for
convenience.
|
nlevels
|
number of contour levels desired iff
levels is not supplied.
|
levels
|
numeric vector of levels at which to draw contour
lines.
|
labcex
|
cex for contour labelling. (not yet used)
|
xlim, ylim
|
x- and y-limits
|
col
|
color for the lines drawn
|
lty
|
line type for the lines drawn
|
add
|
logical. If TRUE, add to a current plot.
|
...
|
additional graphical parameters (see par)
and the arguments to title may also be supplied.
|
Description
Draws contour lines for the desired levels.
There is currently no documentation about the algorithm.
The source code is in `$RHOME/src/main/plot.c'.See Also
image and the graphics demo which can be invoked as
demo(graphics).Examples
x <- -6:16
op <- par(mfrow = c(2, 2))
contour(outer(x, x))
z <- outer(x, sqrt(abs(x)), FUN = "/")
## Should not be necessary:
z[!is.finite(z)] <- NA
image(x, x, z)
contour(x, x, z, col = "pink", add = TRUE)
contour(x, x, z, ylim = c(1, 6))
contour(x, x, z, ylim = c(-6, 6), nlev = 20, lty = 2)
par(op)
## Persian Rug Art:
x <- y <- seq(-4*pi, 4*pi, len = 27)
r <- sqrt(outer(x^2, y^2, "+"))
opar <- par(mfrow = c(2, 2), mar = rep(0, 4))
for(f in pi^(0:3)) contour(cos(r^2)*exp(-r/f))
data("volcano")
rx <- range(x <- 10*1:nrow(volcano))
ry <- range(y <- 10*1:ncol(volcano))
ry <- ry + c(-1,1) * (diff(rx) - diff(ry))/2
tcol <- terrain.colors(12)
par(opar); par(mfrow=c(1,1)); opar <- par(pty = "s", bg = "lightcyan")
plot(x = 0, y = 0,type = "n", xlim = rx, ylim = ry, xlab = "", ylab = "")
u <- par("usr")
rect(u[1], u[3], u[2], u[4], col = tcol[8], border = "red")
contour(x, y, volcano, col = tcol[2], lty = "solid", add = TRUE)
title("A Topographic Map of Maunga Whau", font = 4)
abline(h = 200*0:4, v = 200*0:4, col = "lightgray", lty = 2, lwd = 0.1)
par(opar)