Table 1.
Basic hierarchy data.
Fig 1.
Changes between subsequent time steps in a MeSH hierarchy.
a) A small part of the hierarchy ‘A’ (Anatomy) in 2002. Red links are deleted in the next time step b) The corresponding part of the same hierarchy in 2003. Nodes and links colored red are newly appearing elements.
Fig 2.
Testing W(x) by simulated attachments.
The property x here corresponds to the number of children, and the full symbols connected by continuous lines show the measured W(x) for random attachment (independent of x) in orange (circles), and for preferential attachment with an additive constant (i.e. when a newly added node connects to node i with a probability where a is an arbitrary constant) in blue (squares). Dashed lines correspond to the analytic mean for W(x), whereas the shaded areas indicate the standard deviation around the mean.
Fig 3.
Measuring preference in attachment and detachment events.
In each panel we compare Wemp(x) defined in (8) to the mean and standard deviation of W(x) for random events, given in (9 and 10) and indicated by dashed lines in shaded areas. The pictograms beside the panels show the type of the studied attachment/detachment events and highlight in red whether the given property x was measured on the source or on the target of the links involved in the events. a) Results for the total number of descendants of source nodes in attachments of new links pointing from old nodes to new nodes in hierarchies D (orange) and C (blue). b) Wemp(x) for the number of ancestors of source nodes on new links appearing between old nodes, measured in hierarchies D (orange) and C (blue). c) The same plots when x is equal to the number of ancestors of the target nodes in link deletion events for hierarchies D (orange) and C (blue). d) Wemp(x) in case x is corresponding to the number of ancestors of the target node in attachment of new links between old nodes.
Table 2.
Summary of the results for hierarchy D.
The columns of the table correspond to the studied different link types, and the rows indicate the studied node property on either the source (top 4 rows) or the target (bottom 4 rows). The 3rd, 4th and 5th columns correspond to impossible link types, therefore, are left empty. The entries in the cells correspond to the following abbreviations: ‘s+’, ‘s0’ and ‘s-’ for strong indication of preference, no preference and anti-preference, ‘p+’ and ‘p-’ for indication of preference or anti-preference with a peak, and ‘i.s’ for insufficient statistics.
Table 3.
Based on Table 2. and Tables H-N in S1 Text, the contribution to a given cell is counted according to ‘s+’ = 1, ‘w+’ = ’p+’ = 0.5, ‘s0 = 0’, ‘w–’ = ’p–’ = -0.5, ‘s–’ = -1, and the obtained sum is divided by the number of tables contributing to the given cell. Aggregated cells become ‘i.s’ if more than 3 out of the 7 tables has ‘i.s.’ as well.