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 currently in \$RHOME/src/library/main/plot3d.c.

Usage

contour(x=, y=, z, nlevels = 10,
        levels = pretty(range(z, na.rm = TRUE), nlevels),
        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.
z	a matrix containing the values to be plotted (NAs are allowed).
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)
col	color for the lines drawn
lty	line type for the lines drawn
add	logical. if TRUE, add to a current plot.

See Also

image and the graphics demo which can be invoked as demo(graphics).

Examples

## 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(z= 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)

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