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Risanje vozliščno tranzitivnih grafov : delo diplomskega seminarja
ID Žerdin, Lenart (Author), ID Vidali, Janoš (Mentor) More about this mentor... This link opens in a new window

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Abstract
V delu obravnavamo risanje grafov z visoko stopnjo simetrije, natančneje kubičnih vozliščno tranzitivnih grafov. Klasični algoritmi na osnovi sil, kot sta na primer Eadesov ter Fruchterman–Reingoldov algoritem, pogosto vrnejo zadovoljive slike, vendar simetrije grafa v njih praviloma niso razvidne. Predstavimo prilagoditev Fruchterman–Reingoldovega algoritma, pri kateri poleg grafa podamo tudi njegov avtomorfizem. Vozlišča razporedimo po koncentričnih krožnicah, ki ustrezajo ciklom avtomorfizma, algoritem pa nato optimizira le še polmere in zasuke krožnic, tako da je dobljena slika rotacijsko simetrična glede na podani avtomorfizem. Opišemo tudi metodo, ki za dani graf poišče avtomorfizem, ki po tem postopku vrne čim „lepšo” sliko. Algoritem preizkusimo na grafih iz baze kubičnih vozliščno tranzitivnih grafov in ugotovimo, da najlepše slike tipično dobimo pri avtomorfizmih, ki imajo malo ali nič fiksnih točk in imajo čim daljše cikle.

Language:Slovenian
Keywords:risanje grafov, algoritmi na osnovi sil, vozliščno tranzitivni grafi, avtomorfizem grafa
Work type:Final seminar paper
Typology:2.11 - Undergraduate Thesis
Organization:FMF - Faculty of Mathematics and Physics
Year:2026
PID:20.500.12556/RUL-187894 This link opens in a new window
UDC:519.17:004
COBISS.SI-ID:292242691 This link opens in a new window
Publication date in RUL:16.09.2026
Views:100
Downloads:18
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Secondary language

Language:English
Title:Drawing vertex-transitive graphs
Abstract:
We study the drawing of highly symmetric graphs, more precisely of cubic vertex transitive graphs. Classical force-directed algorithms, such as the Eades algorithm and the Fruchterman–Reingold algorithm, often produce satisfactory pictures, but the symmetries of the graph are usually not visible in them. We present an adaptation of the Fruchterman–Reingold algorithm in which, in addition to the graph, one of its automorphisms is given: the vertices are distributed on concentric circles corresponding to the cycles of the automorphism, and the algorithm then optimizes only the radii and rotations of the circles, so that the resulting drawing is always rotationally symmetric with respect to the given automorphism. We also describe a method which, for a given graph, tries to find an automorphism yielding the „nicest” drawing under this procedure. The algorithm is tested on graphs from the census of cubic vertex-transitive graphs, and we observe that the nicest drawings are typically obtained for automorphisms with few or zero fixed points and long cycles.

Keywords:graph drawing, force-directed algorithms, vertex-transitive graphs, graph automorphism

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