R: Add Points to a Plot

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=1, col="black", 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.

In addition, there is a special set of R plotting symbols which can be obtained with pch=19:25 and can be colored and filled with different colors:

pch=19: solid circle,
pch=20: bullet,
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 colors, palette.

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

Graphical parameters are permitted as arguments to this function.

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)

##-------- Showing all the extra & some char graphics symbols ------------
Pex <- 3 ## now (0.90) 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 = F, 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)
}