pairs
Scatterplot Matrices
A matrix of scatterplots is produced.
 Keywords
 hplot
Usage
pairs(x, ...)
"pairs"(formula, data = NULL, ..., subset, na.action = stats::na.pass)
"pairs"(x, labels, panel = points, ..., lower.panel = panel, upper.panel = panel, diag.panel = NULL, text.panel = textPanel, label.pos = 0.5 + has.diag/3, line.main = 3, cex.labels = NULL, font.labels = 1, row1attop = TRUE, gap = 1, log = "")
Arguments
 x
 the coordinates of points given as numeric columns of a
matrix or data frame. Logical and factor columns are converted to
numeric in the same way that
data.matrix
does.  formula
 a formula, such as
~ x + y + z
. Each term will give a separate variable in the pairs plot, so terms should be numeric vectors. (A response will be interpreted as another variable, but not treated specially, so it is confusing to use one.)  data
 a data.frame (or list) from which the variables in
formula
should be taken.  subset
 an optional vector specifying a subset of observations to be used for plotting.
 na.action
 a function which indicates what should happen
when the data contain
NA
s. The default is to pass missing values on to the panel functions, butna.action = na.omit
will cause cases with missing values in any of the variables to be omitted entirely.  labels
 the names of the variables.
 panel
function(x, y, ...)
which is used to plot the contents of each panel of the display. ...

arguments to be passed to or from methods.
Also, graphical parameters can be given as can arguments to
plot
such asmain
.par("oma")
will be set appropriately unless specified.  lower.panel, upper.panel
 separate panel functions (or
NULL
) to be used below and above the diagonal respectively.  diag.panel
 optional
function(x, ...)
to be applied on the diagonals.  text.panel
 optional
function(x, y, labels, cex, font, ...)
to be applied on the diagonals.  label.pos
y
position of labels in the text panel. line.main
 if
main
is specified,line.main
gives theline
argument tomtext()
which draws the title. You may want to specifyoma
when changingline.main
.  cex.labels, font.labels
 graphics parameters for the text panel.
 row1attop
 logical. Should the layout be matrixlike with row 1 at the top, or graphlike with row 1 at the bottom?
 gap
 distance between subplots, in margin lines.
 log
 a character string indicating if logarithmic axes are to be
used: see
plot.default
.log = "xy"
specifies logarithmic axes for all variables.
Details
The $ij$th scatterplot contains x[,i]
plotted against
x[,j]
. The scatterplot can be customised by setting panel
functions to appear as something completely different. The
offdiagonal panel functions are passed the appropriate columns of
x
as x
and y
: the diagonal panel function (if
any) is passed a single column, and the text.panel
function is
passed a single (x, y)
location and the column name.
Setting some of these panel functions to NULL
is
equivalent to not drawing anything there.
The graphical parameters pch
and col
can be used
to specify a vector of plotting symbols and colors to be used in the
plots.
The graphical parameter oma
will be set by
pairs.default
unless supplied as an argument.
A panel function should not attempt to start a new plot, but just plot
within a given coordinate system: thus plot
and boxplot
are not panel functions.
By default, missing values are passed to the panel functions and will
often be ignored within a panel. However, for the formula method and
na.action = na.omit
, all cases which contain a missing values for
any of the variables are omitted completely (including when the scales
are selected).
References
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
Examples
library(graphics)
pairs(iris[1:4], main = "Anderson's Iris Data  3 species",
pch = 21, bg = c("red", "green3", "blue")[unclass(iris$Species)])
## formula method
pairs(~ Fertility + Education + Catholic, data = swiss,
subset = Education < 20, main = "Swiss data, Education < 20")
pairs(USJudgeRatings)
## show only lower triangle (and suppress labeling for whatever reason):
pairs(USJudgeRatings, text.panel = NULL, upper.panel = NULL)
## put histograms on the diagonal
panel.hist < function(x, ...)
{
usr < par("usr"); on.exit(par(usr))
par(usr = c(usr[1:2], 0, 1.5) )
h < hist(x, plot = FALSE)
breaks < h$breaks; nB < length(breaks)
y < h$counts; y < y/max(y)
rect(breaks[nB], 0, breaks[1], y, col = "cyan", ...)
}
pairs(USJudgeRatings[1:5], panel = panel.smooth,
cex = 1.5, pch = 24, bg = "light blue",
diag.panel = panel.hist, cex.labels = 2, font.labels = 2)
## put (absolute) correlations on the upper panels,
## with size proportional to the correlations.
panel.cor < function(x, y, digits = 2, prefix = "", cex.cor, ...)
{
usr < par("usr"); on.exit(par(usr))
par(usr = c(0, 1, 0, 1))
r < abs(cor(x, y))
txt < format(c(r, 0.123456789), digits = digits)[1]
txt < paste0(prefix, txt)
if(missing(cex.cor)) cex.cor < 0.8/strwidth(txt)
text(0.5, 0.5, txt, cex = cex.cor * r)
}
pairs(USJudgeRatings, lower.panel = panel.smooth, upper.panel = panel.cor)
pairs(iris[5], log = "xy") # plot all variables on log scale
pairs(iris, log = 1:4, # log the first four
main = "Lengths and Widths in [log]", line.main=1.5, oma=c(2,2,3,2))