points                 package: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 `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', 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 `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:

     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)
     }

