span {geosphere} | R Documentation |
Span of polygons
Description
Compute the approximate surface span of polygons in longitude and latitude direction. Span is computed by rasterizing the polygons; and precision increases with the number of 'scan lines'. You can either use a fixed number of scan lines for each polygon, or a fixed band-width.
Usage
span(x, ...)
Arguments
x |
a SpatialPolygons* object or a 2-column matrix (longitude/latitude) |
... |
Additional arguments, see Details |
Details
The following additional arguments can be passed, to replace default values for this function
nbands | Character. Method to determine the number of bands to 'scan' the polygon. Either 'fixed' or 'variable' | |
n | Integer >= 1. If nbands='fixed' , how many bands should be used |
|
res | Numeric. If nbands='variable' , what should the bandwidth be (in degrees)? |
|
fun | Logical. A function such as mean or min. Mean computes the average span | |
... | further additional arguments passed to distGeo | |
Value
A list, or a matrix if a function fun
is specified. Values are in the units of r
(default is meter)
Author(s)
Robert J. Hijmans
Examples
pol <- rbind(c(-180,-20), c(-160,5), c(-60, 0), c(-160,-60), c(-180,-20))
plot(pol)
lines(pol)
# lon and lat span in m
span(pol, fun=max)
x <- span(pol)
max(x$latspan)
mean(x$latspan)
plot(x$longitude, x$lonspan)
[Package geosphere version 1.5-18 Index]