pub fn average_distance(conf: DistConfig) -> Result<f64, NJError>Expand description
Computes the mean of all n*(n-1)/2 unique pairwise distances.
Same alphabet auto-detection and model–alphabet compatibility as [nj].
Returns 0.0 for fewer than 2 taxa. Returns Err for an empty MSA,
incompatible model, or mismatched sequence lengths.