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The definitions of incidence matrix apply to graphs with loops and multiple edges. The column of an oriented incidence matrix that corresponds to a loop is all zero, unless the graph is signed and the loop is negative; then the column is all zero except for ±2 in the row of its incident vertex.

The definitions of incidence matrix apply to graphs with loops and multiple edges. The column of an oriented incidence matrix that corresponds to a loop is all zero, unless the graph is signed and the loop is negative; then the column is all zero except for ±2 in the row of its incident vertex.

'''<font color="#ff8000">多重关联图 Multigraphs</font>'''的定义：多重关联图与循环相对应的定向关联矩阵的列均为零，除非图有符号且循环为负，否则该列除其入射顶点行中的±2外均为零。

'''<font color="#ff8000">多重关联图 Multigraphs</font>'''的定义：多重关联图与循环相对应的定向关联矩阵的列均为零，除了图有符号且循环为负的情况外，该列除其入射顶点行中的±2外均为零。

==Hypergraphs 超图==

==Hypergraphs 超图==