pub fn interpolate(magnitudes: &[f64], bin: usize, span: usize) -> Option<Peak>Expand description
Interpolates the local maximum at bin k of a magnitude spectrum.
With a, b, c = ln|X[k-1]|, ln|X[k]|, ln|X[k+1]| the parabola’s top
sits at delta = 0.5 (a - c) / (a - 2b + c). Returns None when k
has no neighbour on both sides, is not a strict local maximum, or a
magnitude in the three bins is zero. span bins on each side are
searched for a neighbouring peak.