get_tau<-function(cp.table){
  N <- nrow(cp.table);
  iseq <- 1:N;
  tau<-apply(as.matrix(iseq), 2,
             function (i,j) {
                 sqrt((cp.table$x[i] - cp.table$x[j])^2 + (cp.table$y[i] - cp.table$y[j])^2)
             },
             j=1);

   for(j in 2:N) {
       tau <- cbind(tau,
                    apply(as.matrix(iseq), 2,
                          function(i,j) {
                              sqrt((cp.table$x[i]-cp.table$x[j])^2 + (cp.table$y[i]-cp.table$y[j])^2)
                          },
                          j)
                   )
   };
   return (tau);
}


get_tau2<-function(cp.table){
  N <- nrow(cp.table);
  g <- as.matrix(expand.grid(1:N, 1:N))

  tau<-apply(as.matrix(g), 1,
             function (index) {
                 sqrt((cp.table$x[index[1]] - cp.table$x[index[2]])^2 +
                      (cp.table$y[index[1]] - cp.table$y[index[2]])^2)
             }
             );

  return (matrix(tau, nrow=N));
};

get_tau3<-function(cp.table){
  N <- nrow(cp.table);
  iseq <- 1:N;
  sapply(as.list(iseq),
        function(j) {
          f.int <- function (i, j) {
              return(sqrt((cp.table$x[i] - cp.table$x[j])^2 + (cp.table$y[i] - cp.table$y[j])^2))
          }

          return (apply(as.matrix(iseq), 2, f.int, j))
        }
      )
}