points {base}R Documentation

Add Points to a Plot

Description

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.

Usage

points(x, ...)
points.default(x, y=NULL, type="p", pch=par("pch"), col=par("col"),
               bg=NA, cex=1, ...)

Arguments

x, y coordinate vectors of points to plot.
type character indicating the type of plotting; actually any of the types as in plot.
pch plotting ``character'', i.e. symbol to use. pch can either be a character or an integer code for a set of graphics symbols. The full set of S symbols is available with pch=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.
col color code or name, see par.
bg background (``fill'') color for open plot symbols
cex character expansion
... Further graphical parameters (see plot.xy and par) may also be supplied as arguments.

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 are permitted as arguments to this function.

See Also

plot, lines, and the underlying ``primitive'' plot.xy.

Examples

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 <- 1:(np <- 25+11); k <- floor(sqrt(np)); dd <- c(-1,1)/2
rx <- dd + range(ix <- (ipch-1) %/% k)
ry <- dd + range(iy <- 3 + (k-1)-(ipch-1) %% k)
pch <- as.list(ipch)
pch[25+ 1:11] <- 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)
}

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