double xi = D[give_index(i, OTU1, n)]; /* dist between OTU1 and i */
double yi = D[give_index(i, OTU2, n)]; /* dist between OTU2 and i */
double lamb=v[give_index(i,OTU2,n)]/(v[give_index(i,OTU2,n)]+v[give_index(i,OTU1,n)]);
double xi = D[give_index(i, OTU1, n)]; /* dist between OTU1 and i */
double yi = D[give_index(i, OTU2, n)]; /* dist between OTU2 and i */
double lamb=v[give_index(i,OTU2,n)]/(v[give_index(i,OTU2,n)]+v[give_index(i,OTU1,n)]);