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

1 2 3 4 5 6 7 8 9 | ```
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)
``` |

`formula` |
a formula describing the form of conditioning plot. A
formula of the form All three or four variables may be either numeric or factors.
When |

`data` |
a data frame containing values for any variables in the
formula. By default the environment where |

`given.values` |
a value or list of two values which determine how
the conditioning on When there is no |

`panel` |
a |

`rows` |
the panels of the plot are laid out in a |

`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 |

`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 |

`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 |

`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 |

`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 |

`xlim` |
the range for the x axis. |

`ylim` |
the range for the y axis. |

`...` |
additional arguments to the panel function. |

`x` |
a numeric vector. |

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`

.

`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.

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.

`pairs`

,
`panel.smooth`

,
`points`

.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 | ```
## 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)
})
``` |

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