WenJun Zhang School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China; International Academy of Ecology and Environmental Sciences, Hong Kong Network Biology ISSN 2220-8879 http://www.iaees.org/publications/journals/nb/online-version.asp 2015 5 4 137 145 International Academy of Ecology and Environmental Sciences Hong Kong 20 October 2015 5 November 2015 1 December 2015 partial correlation correlation measure Pearson linear correlation Spearman rank correlation algorithm set operation statistic test interaction finding. In the earlier studies, I pointed out that a network changed in a local domain can be approximated as a linear network, i.e., all between-node (or -taxon, -component, etc) changes in the local domain are treated as linear ones and Pearson linear correlation measure can be used. For a little wider domain, the quasi-linear measure, Spearman rank correlation can be used also. In present study, I jointly use Pearson linear correlation measure and Spearman rank correlation measure and their partial correlations to find interactions. First, I define some hierarchical principles for finding interactions. Reliability levels are then defined using set operations. The full algorithm and Matlab codes for finding interactions are given. DOI 10.0000/issn-2220-8879-networkbiology-2015-v5-0011 http://www.iaees.org/publications/journals/nb/articles/2015-5(4)/a-hierarchical-method-for-finding-interactions.pdf