Function hanning 

pub fn hanning(m: usize) -> FerrayResult<Array<f64, Ix1>>

Return the Hann (Hanning) window of length m.

The Hann window is defined as: w(n) = 0.5 * (1 - cos(2pin/(M-1)))

NumPy calls this function hanning. This is equivalent to numpy.hanning(M).

Errors

Returns an error only if internal array construction fails.