Grouping hierarchy issue on level

[Sébastien Heymann]

Grouping nodes with the mouse menu creates an wrong level of hierarchy.

Way to reproduce:

1. Open EuroSiS.gexf : http://wiki.gephi.org/index.php/Datasets
2. Group nodes by the 'country' attribute
3. Select 3 groups with the mouse
4. Right-click and Group them

This group, which contains 3 sub-groups, appears at the level Two instead of being at the top (level Zero).

[Mathieu Bastian (mathieu.bastian)]

No, the group feature is not defining levels like that. It is more the depth than the level actually. The depth of a node is the length of the path to its root.

In your example, when you group with partitions it creates meta-nodes, which are parents of the nodes with the country attribute. Meta-nodes have depth 0 as they are the roots and nodes have depth 1.

When you group three meta-nodes it creates a new meta-node. The three meta-nodes you just grouped have now depth 1. The depth of the untouched meta-node remain zero. The depth of the nodes which are children of the three meta-nodes have the depth incremented as well and become two.

Graph API currently works like this. When working with a tree like we do with hierarchical graphs, using the depth makes much more sense than what you intuitively saw as a level. Having levels like this with unbalanced trees would increase the complexity, but it's certainly possible.

We see here how it is difficult to explore unbalanced hierarchies :-) I would recommend to implement a live dendrogram view like CGV's one to enhance user perception of the hierarchy.

[Sébastien Heymann (sebastien.heymann)]

Okay I see!