Function smoothness_ratio 

pub fn smoothness_ratio(
    graph: &Graph,
    signal: &[f64],
    weights: Option<&[f64]>,
) -> IgraphResult<f64>

Compute the smoothness ratio of a signal on a graph.

SR = 1 - E_D / (2 · Σ_{(u,v)} w · (f(u)² + f(v)²))

Bounded in [0, 1] for non-negative weights. A value of 1 means the signal is perfectly smooth (constant on each connected component); a value of 0 means maximally rough.

Returns 1.0 if the denominator is zero (no edges or all-zero signal).

Examples

use rust_igraph::{Graph, smoothness_ratio};

let g = Graph::from_edges(&[(0,1),(1,2)], false, Some(3)).unwrap();
// Constant signal → perfectly smooth
let sr = smoothness_ratio(&g, &[2.0, 2.0, 2.0], None).unwrap();
assert!((sr - 1.0).abs() < 1e-10);