# maxEarthDist: maximum distance between set of points In brry/OSMscale: Add a Scale Bar to 'OpenStreetMap' Plots

## Description

Maximum great-circle distance between points at lat-long coordinates. This is not computationally efficient. For large datasets, consider pages like http://stackoverflow.com/a/16870359.

## Usage

 `1` ```maxEarthDist(lat, long, data, r = 6371, fun = max, each = TRUE, ...) ```

## Arguments

 `lat, long, data` Coordinates for `earthDist` `r` Earth Radius for `earthDist` `fun` Function to be applied. DEFAULT: `max` `each` Logical: give max dist to all other points for each point separately? If FALSE, will return the maximum of the complete distance matrix, as if `max(maxEarthDist(y,x))`. DEFAULT: TRUE `...` Further arguments passed to fun, like na.rm=TRUE

Single number

## Author(s)

Berry Boessenkool, [email protected], Jan 2017

`earthDist`
 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22``` ```d <- read.table(header=TRUE, text=" x y 14.9 53.73 1.12 53.12 6.55 58.13 7.71 71.44 ") plot(d, asp=1, pch=as.character(1:4), xlab="lon", ylab="lat") for(i in 1:4) segments(d\$x[-i], d\$y[-i], d\$x[i], d\$y[i], col=2) text(x=c(7,10,11), y=c(53,56,64), round(earthDist(y,x,d )[-1]), col=2) text(x=c(4,4), y=c(56,61), round(earthDist(y,x,d,i=2)[3:4]), col=2) text(x=7, y=64, round(earthDist(y,x,d,i=4)[3]), col=2) round( earthDist(y,x,d, i=2) ) round( earthDist(y,x,d, i=3) ) round( maxEarthDist(y,x,d) ) round( maxEarthDist(y,x,d, each=FALSE) ) round( maxEarthDist(y,x,d, fun=min) ) maxEarthDist(y,x, d[1:2,] ) ```