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Display contours

Syntax

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.

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.

See Also

image and the extensive example in system.file("demos/graphics","graphics").

Examples

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) 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)