Parent group of each group, -1 for a top-level group: a hierarchy of groups deeper than one level. Only with hierarchy: 'groups'. Default: none (every group is top level).
hierarchy?
readonly
"groups" | "parents"
What the hierarchy is made of (see the module comment): 'groups' reads graph.group (and groupParent), 'parents' reads graph.parent. Default: 'groups' when the graph has groups, else 'parents' when it has parent. When the graph has neither, or not the one asked for, nothing is bundled.
sameGroupStrength?
readonly
number
Factor on strength for links whose path has 3 points (the two ends have the same parent), 0 to 1, so that links inside a group bend less than links between groups. Default 0.5.
strength?
readonly
number
0 = straight links … 1 = the curve follows the hierarchy path fully. Default 0.85.
