R: return vertex names instead of vertex ids

[gaborcsardi]

From @gaborcsardi on May 4, 2013 18:54

Or, instead of returning a character vector, we could return an igraph.vs. The same for edges.

igraph.vs is a bit tricky, because we don't necessarily want the (potentially big) graph hanging around just because there is an igraph.vs object hanging around somewhere.

An alternative would be to return character vectors with symbolic vertex ids.

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Imported from Launchpad using lp2gh.

• date created: 2012-07-17T18:49:42Z
• owner: gabor.csardi
• assignee: gabor.csardi
• the launchpad url was https://bugs.launchpad.net/bugs/1025828

Copied from original issue: igraph/igraph#113

[gaborcsardi]

(by gabor.csardi)
This change is probably too big for version 0.6, let's postpone it to 0.7.

[gaborcsardi]

With the repaired vs and es indexing returning vs and es seems to be possible. The problem is that these return values cannot be used with modified graph objects. (But they should not be used, anyway.)

But a lot of functions return vertex/edge ids, do we want to change all of them? Here are all of them, unless I forgot some:

• all_shortest_paths
• articulation_points
• bfs
• biconnected_components
• blocks
• canonical_permutation
• cliques
• dfs
• dominator_tree
• ego
• ends
• farthest_vertices
• fit_hrg
• get_diameter
• girth
• graphlet_basis
• graphlets
• groups
• head_of
• incident
• ivs
• largest_cliques
• largest_ivs
• max_cardinality
• max_cliques
• max_flow
• maximal_ivs
• min_cut
• min_separators
• min_st_separators
• neighbors
• predict_edges
• shortest_paths
• st_cuts
• st_min_cuts
• subcomponent
• tail_of
• topo_sort
• triangles
• unfold_tree

[gaborcsardi]

https://github.com/igraph/igraph/tree/return-vs-es

[gaborcsardi]

groups is tricky, because it is not called on the graph. If we want a vs there, then we need to call groups on the graph (as well):

clu <- components(g)
groups(g, clu)

[gaborcsardi]

One big problem is that when one saves an object to a file, the whole graph is saved, too. So returning vs/es is a bad idea..... :( We should return vertex names instead.

[gaborcsardi]

This is mostly sorted out by now, with weak references.

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