Each time search two nodes with lowest weights in an iterative manner
standard graph square matrix
return a matrix in edge form, the first column is the starting node, the second column is the ending node
Youhua Chen <email@example.com>
Chen Y (2012) loop: an R package for performing decomposition of weighted directed graphs, food web analysis and flexible network plotting. Submitted.
Wang HY, Huang Q, Li CZ,Zhu BZ (2010) Graph algorithms and Matlab applications. BUAA Press, Beijing.