R: Generic Function to Add an Axis to a Plot

Axis {graphics} | R Documentation

## Generic Function to Add an Axis to a Plot

### Description

Generic function to add a suitable axis to the current plot.

### Usage

    Axis(x = NULL, at = NULL, ..., side, labels = NULL)

### Arguments

`x` | an object which indicates the range over which an axis should be drawn
`at` | the points at which tick-marks are to be drawn.
`side` | an integer specifying which side of the plot the axis is to be drawn on. The axis is placed as follows: 1=below, 2=left, 3=above and 4=right.
`labels` | this can either be a logical value specifying whether (numerical) annotations are to be made at the tickmarks, or a character or expression vector of labels to be placed at the tickpoints. If this is specified as a character or expression vector, `at` should be supplied and they should be the same length.
`...` | Arguments to be passed to methods and perhaps then to `axis`.

### Details

This is a generic function. It works in a slightly non-standard way: if `x` is supplied and non-NULL it dispatches on `x`, otherwise if `at` is supplied and non-NULL it dispatches on `at`, and the default action is to call `axis`, omitting argument `x`.

The idea is that for plots for which either or both of the axes are numerical but with a special interpretation, the standard plotting functions (including `boxplot`, `contour`, `coplot`, `filled.contour`, `pairs`, `plot.default`, `rug` and `stripchart`) will set up user coordinates and `Axis` will be called to label them appropriately.

There are `"Date"` and `"POSIXt"` methods which can pass an argument `format` on to the appropriate `axis` method (see `axis.POSIXct`).

### Value

The numeric locations on the axis scale at which tick marks were drawn when the plot was first drawn (see ‘Details’).

This function is usually invoked for its side effect, which is to add an axis to an already existing plot.

### See Also

`axis`.

[Package graphics version 3.1.2 Index]