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## Unary Operations

- Complement Trivial, but not available yet (7/19/96).
- Edge Contraction The collapse selected option of the Edit menu replaces all selected items with a single ``super vertex'' sv. Then (u,sv) is an edge if and only if u was not selected, and there exists a vertex v in the subgraph represented by sv such that (u, v) was an edge. A similar argument holds for (sv, u).

  In particular, an edge is contracted by selecting its endpoints with <1st>, then selecting the Collapse Subgraph option or typing s from the keyboard. Super vertices are replaced with the subgraphs they represent by selecting them, then selecting the expand-selected option from the Edit menu or typing S.

- Induced Subgraphs It is very useful sometimes to extract parts of a graph and treat them is graphs themselves. The induced subgraph option of the Edit menu allows the user to extract the subgraph induced by all selected vertices. This operation can also be invoked by selecting the vertices and then typing i on the keyboard.
- Edge-Induced Subgraphs This feature is not implemented yet (7/19/96), but will be used in the same manner as induced-subgraph.
- Line Graph Not available yet (7/19/96).

- Binary Operations

Next: Binary Operations Up: Graph Operations Previous: Graph Operations