rdist.earth {fields} | R Documentation |
Given two sets of longitude/latitude locations computes the Great circle (geographic) distance matrix among all pairings.
rdist.earth(x1, x2, miles = TRUE, R = NULL)
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. |
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.
The great circle distance matrix if nrow(x1)=m and nrow( x2)=n then the returned matrix will be mXn.
rdist, stationary.cov
out<- rdist.earth ( ozone$lon.lat) #out is a 20X20 distance matrix