This help topic is for R version 0.90. For the current version of R, try https://stat.ethz.ch/R-manual/R-patched/library/base/html/contour.html
contour {base}R Documentation

Display Contours

Description

Draws contour lines for the desired levels. There is currently no documentation about the algorithm. The source code is in ‘\$R\_HOME/src/main/plot.c’.

Usage

contour(x = seq(0, 1, len = nrow(z)), y = seq(0, 1, len = ncol(z)),
        z,
        nlevels = 10, levels = pretty(zlim, nlevels),
        xlim = range(x, finite = TRUE),
        ylim = range(y, finite = TRUE),
        zlim = range(z, finite = TRUE),
        labcex = 0,
        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, zlim

x-, y- and z-limits for the plot

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.

See Also

filled.contour for “color-filled” contours, 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)
[Package base version 0.90 ]