A novel quantitative analysis method of genetic relationship of species is presented, which is based on the network composed of 20 nodes corresponding to 20 amino acids and edges corresponding to their interactions. The degree of genetic relationship of species is determined by the distance of the vectors which consist of 40 elements corresponding to the out-degrees and in-degrees of 20 nodes. Compared with the classical methods, it avoids choosing the four reference directions corresponding to four bases of DNA sequence, whose optimal angles are very difficult to get. Moreover, our method is ...
