## Add Points to a Plot

## 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 `type`s 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.

## 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.

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)

    ##-------- Showing all the graphics symbols ------------
    Pex <- if(.Device=="postscript") 5 else 20
    ipch <- 1:25; dd <- c(-1,1)/2
    rx <- dd + range(ix <- (ipch-1) %/% 5)
    ry <- dd + range(iy <- 3 + 4-(ipch-1) %% 5)
    plot(rx, ry, type="n", axes = F, xlab = "", ylab = "",
         main = "plot symbols :  points (..  pch = * )")
    abline(v = ix, h = iy, col = "lightgray", lty = "dotted")
    for(i in ipch) { # red symbols with a yellow interior (where available)
      points(ix[i], iy[i], pch = i, col = "red", bg = "yellow", cex = Pex)
      text(ix[i] - .3, iy[i], i, col = "brown", cex = 1.5)
    }

[Package Contents]