## 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 extra & some char graphics symbols ------------
    Pex <- if(.Device=="postscript") 5 else 20
    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 = "plot symbols :  points (..  pch = * )")
    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 = 1.5)
    }

[Package Contents]