int numNZ();
void sortD(); //Sorts the data in descending order.
void push_front(int, int, string); //abundance, otu, groupname
void insert(int, int, string); //abundance, otu, groupname
int numNZ();
void sortD(); //Sorts the data in descending order.
void push_front(int, int, string); //abundance, otu, groupname
void insert(int, int, string); //abundance, otu, groupname