| points {graphics} | R Documentation |
points is a generic function to draw a sequence of points at
the specified coordinates. The specified character(s) are plotted,
centered at the coordinates.
points(x, ...) ## Default S3 method: points(x, y = NULL, type = "p", ...)
x, y |
coordinate vectors of points to plot. |
type |
character indicating the type of plotting; actually any of
the types as in plot.default. |
... |
Further graphical parameters may also be supplied as arguments. See Details. |
The coordinates can be passed in a plotting structure
(a list with x and y components), a two-column matrix, a
time series, .... See xy.coords.
Graphical parameters commonly used are
pchpch=0:18, see the last picture from example(points),
i.e., the examples below.
In addition, there is a special set of R plotting symbols which
can be obtained with pch=19:25 and 21:25 can be
colored and filled with different colors:
pch=19: solid circle,
pch=20: bullet (smaller circle),
pch=21: circle,
pch=22: square,
pch=23: diamond,
pch=24: triangle point-up,
pch=25: triangle point down.
Values pch=26:32 are currently unused, and pch=32:255
give the text symbol in a single-byte locale. In a multi-byte locale
such as UTF-8, numeric values of pch greater than or equal to
32 specify a Unicode code point (except for the symbol font as
selected by par(font = 5)).
If pch is an integer or character NA or an empty
character string, the point is omitted from the plot.
Value pch="." is handled specially. It is a rectangle of
side 0.01 inch (scaled by cex). In addition, if cex =
1 (the default), each side is at least one pixel (1/72 inch on
the pdf, postscript and
xfig devices).
colpar.bgpch=21:25.cexpar("cex").lwdpar.
Others less commonly used are lty and lwd for
types such as "b" and "l".
Graphical parameters pch, col, bg, cex and
lwd can be vectors (which will be recycled as needed) giving a
value for each point plotted. If lines are to be plotted (e.g. for
type = "b" the first element of lwd is used.
Points whose x, y, pch, col or cex
value is NA are omitted from the plot.
What is meant by ‘a single character’ is locale-dependent.
The encoding may not have symbols for some or all of the characters in
pch=128:255
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
plot, lines, and the underlying
workhorse function plot.xy.
plot(-4:4, -4:4, type = "n")# setting up coord. system
points(rnorm(200), rnorm(200), col = "red")
points(rnorm(100)/2, rnorm(100)/2, col = "blue", cex = 1.5)
op <- par(bg = "light blue")
x <- seq(0,2*pi, len=51)
## something "between type='b' and type='o'":
plot(x, sin(x), type="o", pch=21, bg=par("bg"), col = "blue", cex=.6,
main='plot(..., type="o", pch=21, bg=par("bg"))')
par(op)
##-------- Showing all the extra & some char graphics symbols ------------
Pex <- 3 ## good for both .Device=="postscript" and "x11"
ipch <- 0:35; np <- length(ipch); k <- floor(sqrt(np)); dd <- c(-1,1)/2
rx <- dd + range(ix <- ipch %/% k)
ry <- dd + range(iy <- 3 + (k-1)- ipch %% k)
pch <- as.list(ipch)
pch[26+ 1:10] <- as.list(c("*",".", "o","O","0","+","-","|","%","#"))
plot(rx, ry, type="n", axes = FALSE, xlab = "", ylab = "",
main = paste("plot symbols : points (... pch = *, cex =", Pex,")"))
abline(v = ix, h = iy, col = "lightgray", lty = "dotted")
for(i in 1:np) {
pc <- pch[[i]]
points(ix[i], iy[i], pch = pc, col = "red", bg = "yellow", cex = Pex)
## red symbols with a yellow interior (where available)
text(ix[i] - .3, iy[i], pc, col = "brown", cex = 1.2)
}