# pairs

##### Scatterplot Matrices

A matrix of scatterplots is produced.

- Keywords
- hplot

##### Usage

`pairs(x, …)`# S3 method for formula
pairs(formula, data = NULL, …, subset,
na.action = stats::na.pass)

# S3 method for default
pairs(x, labels, panel = points, …,
horInd = 1:nc, verInd = 1:nc,
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, but`na.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 as`main`

.`par("oma")`

will be set appropriately unless specified.- horInd, verInd
The (numerical) indices of the variables to be plotted on the horizontal and vertical axes respectively.

- 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 the`line`

argument to`mtext()`

which draws the title. You may want to specify`oma`

when changing`line.main`

.- cex.labels, font.labels
graphics parameters for the text panel.

- row1attop
logical. Should the layout be matrix-like with row 1 at the top, or graph-like 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
off-diagonal 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).

Arguments `horInd`

and `verInd`

were introduced in R
3.2.0. If given the same value they can be used to select or re-order
variables: with different ranges of consecutive values they can be
used to plot rectangular windows of a full pairs plot; in the latter
case ‘diagonal’ refers to the diagonal of the full plot.

##### 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))
```

*Documentation reproduced from package graphics, version 3.4.0, License: Part of R 3.4.0*