# segplot {latticeExtra}

### Description

This function can be used to systematically draw segments using a formula interface to produce Trellis displays using the lattice package. Segments can be drawn either as lines or bars, and can be color coded by the value of a covariate, with a suitable legend.

### Usage

segplot(x, data, ...) ## S3 method for class 'formula': segplot((x, data, level = NULL, centers = NULL, prepanel = prepanel.segplot, panel = panel.segplot, xlab = NULL, ylab = NULL, horizontal = TRUE, ..., at, cuts = 30, colorkey = !is.null(level)))

### Arguments

- x
- Argument on which argument dispatch is carried out. For the
`"formula"`

method, a formula of the form`y ~ x1 + x2`

(with further conditioning variables appended if necessary). The terms in the formula must all be vectors of the same length. Each element causes a line segment or rectangle to be drawn, with the vertical location determined by`y`

and horizontal endpoints determined by`x1`

and`x2`

. - data
- An optional data frame, list or environment where variables in the formula, as well as
`level`

, will be evaluated. - level
- An optional covariate that determines color coding of the segments
- centers
- optional vector of ‘centers’ of the segments. If specified, points will be plotted at these
`y`

-locations. - prepanel
- function determining range of the data rectangle from data to be used in a panel.
- panel
- function to render the graphic given the data. This is the function that actually implements the display.
- xlab, ylab
- Labels for the axes. By default both are missing.
- horizontal
- logical, whether the segments are to be drawn horizontally (the default) or vertically. This essentially swaps the role of the x- and y-axes in each panel.
- ...
- further arguments. Arguments to
`levelplot`

as well as to the default panel function`panel.segplot`

can be supplied directly to`segplot`

. - colorkey
- logical indicating whether a legend showing association of segment colors to values of
`level`

should be shown, or a list to control details of such a color key. See details below. - at, cuts
`at`

specifies the values of`level`

where the color code changes. If`at`

is missing, it defaults to`cuts`

equispaced locations spanning the range of`levels`

### Details

The `levelplot`

function from the lattice package is used to internally to implement this function. In particular, the colorkey mechanism is used as it is, and documentation for `levelplot`

should be consulted to learn how to fine tune it.

### Values

An object of class `"trellis"`

. The `update`

method can be used to update components of the object and the `print`

method (usually called by default) will plot it on an appropriate plotting device.

### Note

Currently only horizontal segments are supported. Vertical segments can be obtained by modifying the prepanel and panel functions suitably.

### Examples

segplot(factor(1:10) ~ rnorm(10) + rnorm(10), level = runif(10)) data(USCancerRates) segplot(reorder(factor(county), rate.male) ~ LCL95.male + UCL95.male, data = subset(USCancerRates, state == "Washington")) segplot(reorder(factor(county), rate.male) ~ LCL95.male + UCL95.male, data = subset(USCancerRates, state == "Washington"), draw.bands = FALSE, centers = rate.male) segplot(reorder(factor(county), rate.male) ~ LCL95.male + UCL95.male, data = subset(USCancerRates, state == "Washington"), level = rate.female, col.regions = terrain.colors) segplot(reorder(factor(county), rate.male) ~ LCL95.male + UCL95.male, data = subset(USCancerRates, state == "Washington"), draw.bands = FALSE, centers = rate.male, segments.fun = panel.arrows, ends = "both", angle = 90, length = 1, unit = "mm")

Documentation reproduced from package latticeExtra, version 0.6-28. License: GPL (>= 2)