Function ird_index 

pub fn ird_index(graph: &Graph) -> IgraphResult<f64>

Compute the square-difference irregularity index.

IRD(G) = Σ_{(u,v)∈E} |d(u)² - d(v)²|

Equals 0 for regular graphs. Self-loops are skipped.

Examples

use rust_igraph::{Graph, ird_index};

// K_3: all degrees 2, IRD = 0
let g = Graph::from_edges(&[(0,1),(1,2),(0,2)], false, Some(3)).unwrap();
assert!(ird_index(&g).unwrap().abs() < 1e-10);