Function ecc 

pub fn ecc(
    graph: &Graph,
    eids: Option<&[u32]>,
    k: u32,
    offset: bool,
    normalize: bool,
) -> IgraphResult<Vec<f64>>

Compute the edge clustering coefficient for eids in graph.

• eids = None → every edge (in id order, 0..graph.ecount()).
• eids = Some(&[...]) → just those edges, in the order given.

k must be 3 or 4. offset = true adds the canonical Radicchi +1 to the cycle count; normalize = true divides by the degree-derived maximum.

Edge directions are ignored — the function treats the input as the underlying undirected graph, the same way igraph_ecc does.

Errors

• IgraphError::InvalidArgument when k < 3.
• IgraphError::Unsupported when k > 4 (Radicchi only defines k = 3 and k = 4).
• IgraphError::EdgeOutOfRange when any eid is >= ecount().

Examples

use rust_igraph::{Graph, ecc};

// K_4: every edge sits in 2 triangles, max is 2 → normalised value
// (without offset) is 1.0.
let mut g = Graph::with_vertices(4);
for u in 0..4u32 {
    for v in (u + 1)..4 {
        g.add_edge(u, v).unwrap();
    }
}
let c = ecc(&g, None, 3, false, true).unwrap();
assert_eq!(c, vec![1.0; 6]);