points               package:graphics               R Documentation

_A_d_d _P_o_i_n_t_s _t_o _a _P_l_o_t

_D_e_s_c_r_i_p_t_i_o_n:

     '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.

_U_s_a_g_e:

     points(x, ...)

     ## Default S3 method:
     points(x, y = NULL, type = "p", pch = par("pch"),
            col = par("col"), bg = NA, cex = 1, ...)

_A_r_g_u_m_e_n_t_s:

    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 single character or an integer code for one of 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.

          Values 'pch=26:32' are currently unused, and 'pch=32:255'
          give the text symbol in a single-byte locale.  In a
          multi-byte locale such as UTF-8, numeric values of 'pch'
          greater than or equal to 32 specify a Unicode code point.

          If 'pch' is an integer or character 'NA' or an empty
          character string, the point is omitted from the plot.

          Value 'pch="."' is handled specially.  It is a rectangle of
          side 0.01 inch (scaled by 'cex').  In addition, if 'cex = 1'
          (the default), each side is at least one pixel (1/72 inch on
          the 'pdf', 'postscript' and 'xfig' devices).  The details
          here have been changed for 2.1.0 and are subject to change. 

     col: color code or name, see 'par'.

      bg: background ("fill") color for open plot symbols

     cex: character (or symbol) expansion: a numerical vector.

     ...: Further graphical parameters (see 'plot.xy' and 'par') may
          also be supplied as arguments.

_D_e_t_a_i_l_s:

     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'.

     Arguments 'pch', 'col', 'bg', 'cex' and 'lwd' can be vectors
     (which will be recycled as needed) giving a value for each point
     plotted. Points whose 'x', 'y', 'pch', 'col' or 'cex' value is
     'NA' are omitted from the plot.

     Graphical parameters are permitted as arguments to this function.

_N_o_t_e:

     What is meant by 'a single character' is locale-dependent.

     The encoding may not have symbols for some or all of the
     characters in 'pch=128:255'

_R_e_f_e_r_e_n_c_e_s:

     Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) _The New S
     Language_. Wadsworth & Brooks/Cole.

_S_e_e _A_l_s_o:

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

_E_x_a_m_p_l_e_s:

     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)
     }

