rdist.earth {fields} R Documentation

## Great circle distance matrix

### Description

Given two sets of longitude/latitude locations computes the Great circle (geographic) distance matrix among all pairings.

### Usage

```rdist.earth(x1, x2, miles = TRUE, R = NULL)
```

### Arguments

 `x1` Matrix of first set of lon/lat coordinates first column is the longitudes and second is the latitudes. `x2` Matrix of second set of lon/lat coordinates first column is the longitudes and second is the latitudes. If missing x1 is used. `miles` If true distances are in statute miles if false distances in kilometers. `R` Radius to use for sphere to find spherical distances. If NULL the radius is either in miles or kilometers depending on the values of the miles argument. If R=1 then distances are of course in radians.

### Details

Surprisingly this all done efficiently in R by dot products of the direction cosines. Thanks to Qing Yang for pointing this out a long time ago.

### Value

The great circle distance matrix if nrow(x1)=m and nrow( x2)=n then the returned matrix will be mXn.

```out<- rdist.earth ( ozone\$lon.lat)