points {graphics} | R Documentation |
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.
points(x, ...)
## Default S3 method:
points(x, y = NULL, type = "p", ...)
x , y |
coordinate vectors of points to plot. |
type |
character indicating the type of plotting; actually any of
the |
... |
Further graphical parameters may also be supplied as arguments. See ‘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
. If supplied
separately, they must be of the same length.
Graphical parameters commonly used are
pch
plotting ‘character’, i.e., symbol to use.
This 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 examples below.
Value pch="."
(equivalently pch = 46
) 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).
For other text symbols, cex = 1
corresponds to the default
fontsize of the device, often specified by an argument
pointsize
. For pch
in 0:25
the default size
is about 75% of the character height (see par("cin")
).
col
color code or name, see par
.
bg
background (fill) color for the open plot
symbols given by pch=21:25
.
cex
character (or symbol) expansion: a numerical vector.
This works as a multiple of par("cex")
.
lwd
line width for drawing symbols see par
.
Others less commonly used are lty
and lwd
for
types such as "b"
and "l"
.
Graphical parameters 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.
Values of pch
are stored internally as integers. The
interpretation is
NA_integer_
: no symbol.
0:18
: S-compatible vector symbols.
0:25
: R vector symbols.
26:31
: unused (and ignored).
32:127
: ASCII characters.
128:255
native characters only in a
single-byte locale and for the symbol font. (128:159
are
only used on Windows.)
-32 ...
Unicode point (where supported).
Note that unlike S (which uses octagons), symbols 1
, 10
,
13
and 16
use circles. The filled shapes do not include
a border.
The following R plotting symbols are can be obtained with
pch=19:25
: those with 21:25
can be colored and
filled with different colors: col
gives the border color
and bg
the background color.
pch=19
: solid circle,
pch=20
: bullet (smaller circle),
pch=21
: filled circle,
pch=22
: filled square,
pch=23
: filled diamond,
pch=24
: filled triangle point-up,
pch=25
: filled triangle point down.
Note that all of these both fill the shape and draw a border. Some
care in interpretation is needed when semi-transparent colours are
used for both fill and border (and the result might be device-specific
and even viewer-specific for pdf
).
Values pch=26:31
are currently unused and pch=32:127
give the ASCII characters. In a single-byte locale
pch=128:255
give the corresponding character (if any) in
the locale's character set. Where supported by the OS, negative
values specify a Unicode point, so e.g. -0x2642L
is a ‘male sign’ and -0x20ACL
is the Euro.
A character string consisting of a single character is converted to an
integer: 32:127
for ASCII characters, and usually to the
Unicode point number otherwise. (In non-Latin-1 single-byte locales,
128:255
will be used for 8-bit characters.)
If pch
supplied is a logical, integer or character
NA
or an empty character string the point is omitted from
the plot.
If pch
is NULL
or otherwise of length 0,
par("pch")
is used.
If the symbol font (par(font = 5)
) is used, numerical
values should be used for pch
: the range is
c(32:126, 160:254)
in all locales (but 240
is not
defined (used for ‘apple’ on Mac OS) and 160
, Euro, may
not be present).
A single-byte encoding may include the characters in
pch=128:255
, and if it does, a font may not include all (or
even any) of them.
Not all negative numbers are valid as Unicode points, and no check is done. A display device is likely to use a rectangle for (or omit) Unicode points that do not exist or which it does not have a glyph.
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
plot
, lines
, and the underlying
workhorse function plot.xy
.
require(stats) # for rnorm
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 ---------
pchShow <-
function(extras = c("*",".", "o","O","0","+","-","|","%","#"),
cex = 3, ## good for both .Device=="postscript" and "x11"
col = "red3", bg = "gold", coltext = "brown", cextext = 1.2,
main = paste("plot symbols : points (... pch = *, cex =",
cex,")"))
{
nex <- length(extras)
np <- 26 + nex
ipch <- 0:(np-1)
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) # list with integers & strings
if(nex > 0) pch[26+ 1:nex] <- as.list(extras)
plot(rx, ry, type="n", axes = FALSE, xlab = "", ylab = "",
main = main)
abline(v = ix, h = iy, col = "lightgray", lty = "dotted")
for(i in 1:np) {
pc <- pch[[i]]
## 'col' symbols with a 'bg'-colored interior (where available) :
points(ix[i], iy[i], pch = pc, col = col, bg = bg, cex = cex)
if(cextext > 0)
text(ix[i] - 0.3, iy[i], pc, col = coltext, cex = cextext)
}
}
pchShow()
pchShow(c("o","O","0"), cex = 2.5)
pchShow(NULL, cex = 4, cextext = 0, main = NULL)
## ------------ test code for various pch specifications -------------
# Try this in various font families (including Hershey)
# and locales. Use sign=-1 asserts we want Latin-1.
# Standard cases in a MBCS locale will not plot the top half.
TestChars <- function(sign=1, font=1, ...)
{
if(font == 5) { sign <- 1; r <- c(32:126, 160:254)
} else if (l10n_info()$MBCS) r <- 32:126 else r <- 32:255
if (sign == -1) r <- c(32:126, 160:255)
par(pty="s")
plot(c(-1,16), c(-1,16), type="n", xlab="", ylab="",
xaxs="i", yaxs="i")
grid(17, 17, lty=1)
for(i in r) try(points(i%%16, i%/%16, pch=sign*i, font=font,...))
}
TestChars()
try(TestChars(sign=-1)) # needs MBCS support
TestChars(font=5) # Euro might be at 160. Mac OS has apple at 240.