R: Add Scale to Existing Unprojected Map

map.scale {maps} | R Documentation

## Add Scale to Existing Unprojected Map

### Description

Adds a scale to an existing map, both as a ratio and a distance gauge.

### Usage

    map.scale(x, y, relwidth = 0.15, metric = TRUE, ratio = TRUE, ...)

### Arguments

`x` |
`y` | Location of left end of distance gauge. If not specified, this will be taken to be near the lower left corner of the map.
`relwidth` | Proportion of width of display to be used for the scale. The default is 0.15 (15%).
`metric` | If `TRUE`, the distance gauge will be in km, otherwise miles.
`ratio` | If `FALSE`, the scale ratio of the map is not displayed.
`...` | Further plotting parameters may be specified as for the command text().

### Details

The scale is calculated from the displayed graph's plotting parameters, and the latitude of the location at which the distance gauge will be displayed.

### Value

The exact calculated scale is returned.

### NOTE

This function is meaningful only if no projection= has been specified in the call to map().

### Side Effects

A scale is added to the currently displayed map. This takes the form of an approximate 1:n scale (containing 2-3 significant digits), above a distance gauge which is reasonably accurate for the latitude at which it appears. The circumference at the given latitude is interpolated from a radius of 6356.78 km at the pole and 6378.16 km at the equator.

### See Also

`map.axes`

### Examples

    map("world", "China")
    map.scale()

[Package maps version 3.3.0 Index]