计算两点之间的距离

euc.dist <- function(x1, x2) sqrt(sum((x1 - x2) ^ 2))

library(foreach)
foreach(i = 1:nrow(x1), .combine = c ) %do% euc.dist(x1[i,],x2[i,])

from https://stackoverflow.com/questions/24746892/how-to-calculate-euclidian-distance-between-two-points-defined-by-matrix-contain