Function degree_distance 

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

Compute the degree-distance index (Schultz-type).

DD(G) = Σ_{u≠v} (deg(u) + deg(v)) · d(u, v)

For connected graphs only; disconnected pairs are skipped.

Examples

use rust_igraph::{Graph, degree_distance};

// Path 0-1-2: degrees [1,2,1]
// pairs: (0,1) d=1 (1+2)=3, (0,2) d=2 (1+1)=2·2=4,
//        (1,0) d=1 3, (1,2) d=1 3, (2,0) d=2 4, (2,1) d=1 3
// DD = 3+4+3+3+4+3 = 20
let g = Graph::from_edges(&[(0,1),(1,2)], false, Some(3)).unwrap();
assert_eq!(degree_distance(&g).unwrap(), 20);