## Conditioning Plots

## Usage

    coplot(formula, data, given.values, panel = points, rows, columns,
           show.given = TRUE, col = par("fg"), pch = par("pch"), ...)
    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`. `x` and lang(y) must be numeric, but `a` and `b` may be either numeric or factors.
`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. Usually this is a matrix with two columns which each row of which gives and 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).
`panel` | a function 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` | should conditioning plots be shown for the 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 recycyled.
`...` | additional arguments to the panel function.
`number` | the number conditioning intervals.
`overlap` | the fraction of overlap of the conditioning variables.

## Description

This function produces two variants of the conditioning plots discussed in the reference below.

## References

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

## See Also

`pairs`, `panel.smooth`, `points`.

## Examples

    ## Tonga Trench Earthquakes
    data(quakes)
    coplot(long ~ lat | depth, data = quakes)
    coplot(long ~ lat | depth * mag, data = quakes)

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