Function second_gourava_index 

pub fn second_gourava_index(graph: &Graph) -> IgraphResult<u64>

Compute the second Gourava index.

GO₂(G) = Σ_{(u,v)∈E} (d(u)+d(v)) · (d(u)·d(v))

Self-loops are skipped.

Examples

use rust_igraph::{Graph, second_gourava_index};

// K_3: each edge (2+2)·(2·2) = 4·4 = 16, 3 edges → 48
let g = Graph::from_edges(&[(0,1),(1,2),(0,2)], false, Some(3)).unwrap();
assert_eq!(second_gourava_index(&g).unwrap(), 48);