R: Calculate aspect ratio for plotting geographic maps; create...

mapasp {sp} | R Documentation

## Calculate aspect ratio for plotting geographic maps; create nice degree axis labels

### Description

Calculate aspect ratio for plotting geographic maps; create nice degree axis labels

### Usage

    mapasp(data, xlim, ylim)
    degreeLabelsEW(x)
    degreeLabelsNS(x)

### Arguments

`data` | object of class or extending `Spatial`
`xlim` | the xlim argument passed (or derived from bounding box)
`ylim` | the ylim argument passed (or derived from bounding box)
`x` | numeric; values at which tics and marks will be generated

### Value

`mapasp` is used for the aspect argument in lattice plots and spplot;

let x = dy/dx, with dy and dx the y- and x-size of the map.

let s = 1/cos((My * pi)/180) with My the y coordinate of the middle of the map (the mean of ylim)

for latlong (longlat) data, `mapasp` returns s * x. for other data, mapasp returns "iso".

### Note

the values for `x` are typically obtained from axTicks

### See Also

levelplot in package `lattice`

[Package sp version 1.4-5 Index]