Szeged Index Calculator

distance-partitioning index

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About Szeged Index Calculator

A Szeged index calculator computing Sz(G) = Σ_{e=(i,j)} n_i(e)·n_j(e) where n_i(e) = vertices closer to i than j. Gutman (1994). Generalization of Wiener index for non-trees. Sz ≥ W always. Sz = W iff bipartite. Client-side.

Szeged Index Calculator Features

  • Sz(G)
  • nᵢ·nⱼ
  • ≥ Wiener
  • Bipartite
  • Common graphs
Szeged index Sz(G) = Σ nᵢ(e)·nⱼ(e). For each edge e=(i,j): count vertices closer to i vs closer to j. Multiply counts. Sum over all edges. Gutman (1994). Sz ≥ W (Wiener) always. Sz = W iff G is bipartite (no odd cycles)!

How to Use

Select graph:

  • Sz: Szeged index
  • nᵢ·nⱼ: Per edge
  • Sz vs W: Compare

Sz vs Wiener

For trees: Sz = W (bipartite, no equidistant vertices). For non-bipartite: Sz > W. The gap Sz-W measures 'non-bipartiteness'. The revised Szeged index also counts equidistant vertices.

Applications

QSAR: Sz correlates with molecular properties. Network analysis: edge-centric distance measure. Captures how each edge 'divides' the graph into two sides. Graph partitioning quality metric.

Step-by-Step Instructions

  1. 1Select graph.
  2. 2For each edge: count nᵢ, nⱼ.
  3. 3Multiply nᵢ·nⱼ.
  4. 4Sum over edges.
  5. 5Compare with W.

Szeged Index Calculator — Frequently Asked Questions

Why is Sz ≥ W always?+

For trees, every vertex is strictly closer to one endpoint (bipartite). For non-trees, some vertices are equidistant — they don't count in nᵢ or nⱼ. This 'missing' contribution makes W use smaller factors.

What does nᵢ(e) mean?+

For edge e=(u,v): nᵤ(e) = number of vertices w with d(w,u) < d(w,v). These vertices are 'on u's side' of the edge. The edge divides the graph into two influence zones.

What is the revised Szeged index?+

Revised Sz: vertices equidistant to both endpoints are split equally between nᵢ and nⱼ. Fixes the 'missing vertex' problem. For bipartite: unchanged. For non-bipartite: Sz_rev < Sz.

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