| contour {base} | R Documentation |
Create a contour plot, or add contour lines to an existing plot.
contour(x = seq(0, 1, len = nrow(z)), y = seq(0, 1, len = ncol(z)),
z,
nlevels = 10, levels = pretty(zlim, nlevels), labels = NULL,
xlim = range(x, finite = TRUE),
ylim = range(y, finite = TRUE),
zlim = range(z, finite = TRUE),
labcex = 0.6, drawlabels = TRUE, method = "flattest",
vfont = c("sans serif", "plain"),
col = par("fg"), lty = par("lty"), lwd = par("lwd"),
add = FALSE, ...)
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. |
labels |
a vector giving the labels for the contour lines. If
NULL then the levels are used as labels. |
labcex |
cex for contour labelling. |
drawlabels |
logical. Contours are labelled if TRUE. |
method |
character string specifying where the labels will be
located. Possible values are "simple", "edge" and
"flattest" (the default). See the Details section. |
vfont |
if a character vector of length 2 is specified, then Hershey
vector fonts are used for the contour labels.
The first element of the vector
selects a typeface and the second element selects a fontindex
(see text for more information). |
xlim, ylim, zlim |
x-, y- and z-limits for the plot. |
col |
color for the lines drawn. |
lty |
line type for the lines drawn. |
lwd |
line width 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. |
There is currently no documentation about the algorithm. The source code is in `$R_HOME/src/main/plot3d.c'.
The methods for positioning the labels on contours are "simple"
(draw at the edge of the plot, overlaying the contour line),
"edge" (draw at the edge of the plot, embedded in the contour
line, with no labels overlapping) and "flattest"
(draw on the flattest section of the contour, embedded in the
contour line, with no labels overlapping). The second and third may
not draw a label on every contour line.
For information about vector fonts, see the
help for text and Hershey.
filled.contour for ``color-filled'' contours,
image and the graphics demo which can be invoked as
demo(graphics).
x <- -6:16
op <- par(mfrow = c(2, 2))
contour(outer(x, x), method = "edge", vfont = c("sans serif", "plain"))
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, method = "edge",
vfont = c("sans serif", "plain"))
contour(x, x, z, ylim = c(1, 6), method = "simple", labcex = 1)
contour(x, x, z, ylim = c(-6, 6), nlev = 20, lty = 2, method = "simple")
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), drawlabels = 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,
vfont = c("sans serif", "plain"))
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)