Selection of this option brings up a heading VERTEX INFORMATION in the right-hand panel plus certain sub-headings. Five options are available below : CURSOR, INDEX, COORD, ERASE SOME, QUIT. The first three give means of selecting the vertex (node) for which information is required.
Depending on the user's choice of means for indicating the node (vertex) for which information is required, other prompts follow. Eventually, the following information on the selected node appears:
- index number
- computational code
- list of neighbours.
A marker is placed at each vertex examined. If a number of points are examined, it may be desirable to erase existing markers in order to be able to spot new markers. ERASE SOME erases all but the last marker created.
After choosing a node, the user may change its depth, computational code or coordinates by Picking the corresponding current values shown in red in the right-hand panel. It is advisable not to change the coordinates of a vertex unless it is visible, so as to avoid impermissible moves of the types shown in Figure 5.3. It should be noted that using this option to make the coordinates of a vertex identical (or nearly identical) to those of a neighbour does not result in a MERGE operation, and this type of change should be avoided.