Shifted Sine-Bell Apodization
Functional form:
sp(x_i) = sin( (pi*off + pi*(end-off)*i/(size-1) )**pow
Parameters:
- data Array of spectral data.
- start Start of Sine-Bell as percent of vector (0.0 -> 1.0)
- end End of Sine-Bell as percent of vector (0.0 -> 1.0 )
- pow Power of Sine-Bell
- inv Set True for inverse apodization.