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Display Contours
Usage
contour(x=, y=, z, nlevels = 10,
levels = pretty(range(z, na.rm = TRUE), nlevels),
labcex = 0,
xlim = range(x), ylim = range(y),
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)
|
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.
|
Description
Draws contour lines for the desired levels.
There is currently no documentation about the algorithm.
The source code is in $RHOME/src/main/plot3d.c.
See Also
image
and the graphics demo which can be invoked as
demo(graphics)
.
Examples
x <- -6:16 ; z <- outer(x, sqrt(abs(x)), FUN="/")
op <- par(mfrow=c(2,2))
contour(z=outer(x, x))
image(x,x, z)
contour(x,x, z, col="pink", add=T)
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(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)