pub fn chebwin(m: usize, at: f64) -> FerrayResult<Array<f64, Ix1>>Expand description
Dolph–Chebyshev window with sidelobe attenuation at dB (#740).
Mirrors scipy.signal.windows.chebwin. The window is the
inverse Fourier transform of the (M-1)-th Chebyshev polynomial
of the first kind evaluated on a cosine sweep, producing an
equiripple sidelobe response at at dB below the main lobe.
Implemented via direct DFT (sufficient for typical M ≤ 1024; the inner loop is O(M²) but allocation-free). Result is normalised so the centre value is 1.
§Errors
FerrayError::InvalidValue if at is non-finite or
at <= 0.0. m == 0 returns the empty window; m == 1
returns [1.0].