SIMPLE CONSTRUCTION OF EMBEDDING FREQUENCIES OF TREES AND ROOTED TREES

A unified approach for the calculation of embedding frequencies of tre es as well as rooted trees is suggested. It consists of a simple pruni ng process when marginal vertices are successively removed. The proble m of isomorphism between (rooted) trees is solved by making use of Rea d's linear canonical code. Simple criteria, based on the concept of va lence vectors, for verification whether a (rooted) tree can be a subtr ee of a (rooted) tree are proved. Tables of embedding frequencies of t rees and rooted trees through ten and eight vertices, respectively, ar e presented. The embedding frequencies of rooted trees are useful for construction of descriptors of molecular graphs when the so-called loc al properties are studied.