Second nearest neighbor with crossdist using apply()

nncross2.R

#get pairwise distances from rp and ponderosa datasets
xpairs <- crossdist(rp, ponderosa) 

#A function to get the second nearest neighbor
nncross2 <- function (x) sort(x)[2] 

#Initialize the vector container for x.2
x.2 <- numeric() 

#Applies the nncross2 function to the xpairs matrix.
x.2 <- apply(xpairs, 1, nncross2)