Deleting objects

A vertex or an edge may be deleted by selecting DELETE on the panel, pointing the mouse at the vertex or edge, and clicking the left button. Do not delete vertex 0, since this is the start vertex, and any new vertices added will have numbers higher than the current highest numbered vertex. That is, once a vertex is deleted, its number will not be reassigned to newly created vertices. The pull-down menu (right mouse button) also has a CLEAR option, which deletes the whole graph and starts from scratch.