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→Multigraphs
==Multigraphs==
==Multigraphs==
'''<font color="#ff8000">多重图 Multigraphs</font>'''
'''<font color="#ff8000">多重图 Multigraphs</font>'''<br>
The definitions of incidence matrix apply to graphs with [[loop (graph theory)|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 [[loop (graph theory)|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.