Matrix graph

Matrix graph --- граф матрицы.

For an [math]\displaystyle{ n \times n }[/math] real symmetric matrix [math]\displaystyle{ A }[/math], the graph [math]\displaystyle{ G(A) = (V,E) }[/math] of [math]\displaystyle{ A }[/math] is defined by: [math]\displaystyle{ V(G) = \{1, \ldots, n\} }[/math] and [math]\displaystyle{ E(G) = \{(i,j): \; i \neq j, \; a_{ij} \neq 0, \; i,j = 1, \ldots, n\} }[/math].