Node
GhtErr ght_node_set_z_avg(GhtNode *node, double z_avg)
GhtErr ght_node_get_z_avg(const GhtNode *node, double *z_avg)
GhtErr ght_node_calculate_z(const GhtNode *node, GhtAttribute *attr)
static double ght_node_z_avg(const GhtNode *node)

Tree
GhtErr ght_tree_calculate_z_average(const GhtTree *tree)
GhtErr ght_tree_get_root(const GhtTree *tree, GhtNode **root)

Internal
Add attribut z_avg

GHT.H
GhtErr ght_tree_get_root(const GhtTreePtr tree, GhtNodePtr *root);
GhtErr ght_tree_calculate_z_average(const GhtTreePtr tree
GhtErr ght_node_get_z_avg(const GhtNodePtr node, double *z_avg)