# coplot

##### Conditioning Plots

This function produces two variants of the **co**nditioning plots
discussed in the reference below.

##### Usage

```
coplot(formula, data, given.values, panel = points, rows, columns,
show.given = TRUE, col = par("fg"), pch = par("pch"),
bar.bg = c(num = gray(0.8), fac = gray(0.95)),
xlab = c(x.name, paste("Given :", a.name)),
ylab = c(y.name, paste("Given :", b.name)),
subscripts = FALSE,
axlabels = function(f) abbreviate(levels(f)),
number = 6, overlap = 0.5, xlim, ylim, …)
co.intervals(x, number = 6, overlap = 0.5)
```

##### Arguments

- formula
a formula describing the form of conditioning plot. A formula of the form

`y ~ x | a`

indicates that plots of`y`

versus`x`

should be produced conditional on the variable`a`

. A formula of the form`y ~ x| a * b`

indicates that plots of`y`

versus`x`

should be produced conditional on the two variables`a`

and`b`

.All three or four variables may be either numeric or factors. When

`x`

or`y`

are factors, the result is almost as if`as.numeric()`

was applied, whereas for factor`a`

or`b`

, the conditioning (and its graphics if`show.given`

is true) are adapted.- data
a data frame containing values for any variables in the formula. By default the environment where

`coplot`

was called from is used.- given.values
a value or list of two values which determine how the conditioning on

`a`

and`b`

is to take place.When there is no

`b`

(i.e., conditioning only on`a`

), usually this is a matrix with two columns each row of which gives an interval, to be conditioned on, but is can also be a single vector of numbers or a set of factor levels (if the variable being conditioned on is a factor). In this case (no`b`

), the result of`co.intervals`

can be used directly as`given.values`

argument.- panel
a

`function(x, y, col, pch, …)`

which gives the action to be carried out in each panel of the display. The default is`points`

.- rows
the panels of the plot are laid out in a

`rows`

by`columns`

array.`rows`

gives the number of rows in the array.- columns
the number of columns in the panel layout array.

- show.given
logical (possibly of length 2 for 2 conditioning variables): should conditioning plots be shown for the corresponding conditioning variables (default

`TRUE`

).- col
a vector of colors to be used to plot the points. If too short, the values are recycled.

- pch
a vector of plotting symbols or characters. If too short, the values are recycled.

- bar.bg
a named vector with components

`"num"`

and`"fac"`

giving the background colors for the (shingle) bars, for**num**eric and**fac**tor conditioning variables respectively.- xlab
character; labels to use for the x axis and the first conditioning variable. If only one label is given, it is used for the x axis and the default label is used for the conditioning variable.

- ylab
character; labels to use for the y axis and any second conditioning variable.

- subscripts
logical: if true the panel function is given an additional (third) argument

`subscripts`

giving the subscripts of the data passed to that panel.- axlabels
function for creating axis (tick) labels when x or y are factors.

- number
integer; the number of conditioning intervals, for a and b, possibly of length 2. It is only used if the corresponding conditioning variable is not a

`factor`

.- overlap
numeric < 1; the fraction of overlap of the conditioning variables, possibly of length 2 for x and y direction. When overlap < 0, there will be

*gaps*between the data slices.- xlim
the range for the x axis.

- ylim
the range for the y axis.

- …
additional arguments to the panel function.

- x
a numeric vector.

##### Details

In the case of a single conditioning variable `a`

, when both
`rows`

and `columns`

are unspecified, a ‘close to
square’ layout is chosen with `columns >= rows`

.

In the case of multiple `rows`

, the *order* of the panel
plots is from the bottom and from the left (corresponding to
increasing `a`

, typically).

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.

The rendering of arguments `xlab`

and
`ylab`

is not controlled by `par`

arguments
`cex.lab`

and `font.lab`

even though they are plotted by
`mtext`

rather than `title`

.

##### Value

`co.intervals(., number, .)`

returns a (`number`

\(\times\)
2) `matrix`

, say `ci`

, where `ci[k,]`

is
the `range`

of `x`

values for the `k`

-th interval.

##### References

Chambers, J. M. (1992)
*Data for models.*
Chapter 3 of *Statistical Models in S*
eds J. M. Chambers and T. J. Hastie, Wadsworth & Brooks/Cole.

Cleveland, W. S. (1993) *Visualizing Data.* New Jersey: Summit Press.

##### See Also

##### Examples

`library(graphics)`

```
## Tonga Trench Earthquakes
coplot(lat ~ long | depth, data = quakes)
given.depth <- co.intervals(quakes$depth, number = 4, overlap = .1)
coplot(lat ~ long | depth, data = quakes, given.v = given.depth, rows = 1)
## Conditioning on 2 variables:
ll.dm <- lat ~ long | depth * mag
coplot(ll.dm, data = quakes)
coplot(ll.dm, data = quakes, number = c(4, 7), show.given = c(TRUE, FALSE))
coplot(ll.dm, data = quakes, number = c(3, 7),
overlap = c(-.5, .1)) # negative overlap DROPS values
## given two factors
Index <- seq(length = nrow(warpbreaks)) # to get nicer default labels
coplot(breaks ~ Index | wool * tension, data = warpbreaks,
show.given = 0:1)
coplot(breaks ~ Index | wool * tension, data = warpbreaks,
col = "red", bg = "pink", pch = 21,
bar.bg = c(fac = "light blue"))
## Example with empty panels:
with(data.frame(state.x77), {
coplot(Life.Exp ~ Income | Illiteracy * state.region, number = 3,
panel = function(x, y, ...) panel.smooth(x, y, span = .8, ...))
## y ~ factor -- not really sensible, but 'show off':
coplot(Life.Exp ~ state.region | Income * state.division,
panel = panel.smooth)
})
```

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

### Community examples

**mark@niemannross.com**at Oct 5, 2018 graphics v3.5.1

```r coplot(ChickWeight$weight ~ ChickWeight$Time | ChickWeight$Diet) coplot(weight ~ Time | Diet, data = ChickWeight) coplot(weight ~ Time | Diet, data = ChickWeight, columns = 4) coplot(weight ~ Time | Diet, data = ChickWeight, panel = function(x,y,...) { abline(lm(y ~ x)) }) # video tutorial at http://niemannross.com/link/coplot ```