coplot {graphics} | R Documentation

## Conditioning Plots

### Description

This function produces two variants of the conditioning 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 numeric and factor 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` x 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

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

### Examples

    ## 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)
    })

[Package graphics version 3.3.2 Index]