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
          (except for the symbol font as selected by 'par(font = 5)').

          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 given by
          'pch=21:25'.

     cex: character (or symbol) expansion: a numerical vector. This
          works as a multiple of 'par("cex")'.

     ...: 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.  If lines are to be plotted (e.g. for 'type = "b"' the
     first element of 'lwd' is used.

     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 <- 0:35; np <- length(ipch); k <- floor(sqrt(np)); dd <- c(-1,1)/2
     rx <- dd + range(ix <- ipch %/% k)
     ry <- dd + range(iy <- 3 + (k-1)- ipch %% k)
     pch <- as.list(ipch)
     pch[26+ 1:10] <- 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)
     }

