计算两类拉特隆点之间的距离

Question

I have a series of latlong coordinates in R which are divided among two individuals:

name   lat         long
A      -28.63784   28.69085
A      -28.65366   28.70843
A      -28.80918   28.94223
B      -26.71335   22.80713
B      -26.75022   20.58426
B      -34.37791   20.51215

How do I calculate the distance between the coordinates of one individual to the other but not to itself? I've looked at similar questions on here but I can't see anything that will do the grouping for me.

Thanks

Answer 1

First create two lon/lat data frames, one for individual A and one for B :

locationsA <- subset(d, name == "A", select = c("long", "lat"))
locationsB <- subset(d, name == "B", select = c("long", "lat"))

The rdist.earth function in the fields package can then compute the matrix of distances of all pairings:

library(fields)
dists <- rdist.earth(locationsA, locationsB)

For the six rows you showed, for example, these distances are (in miles):

         [,1]     [,2]     [,3]
[1,] 384.1700 513.2758 624.3275
[2,] 385.5346 514.5599 624.4023
[3,] 402.4771 530.8293 628.1450