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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 (NA s 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)