Function unit_norm_range 

pub fn unit_norm_range(
    series: &[FloatType],
    fix_range: Option<&[FloatType]>,
) -> Vec<FloatType> 

Numbers spaced across the unit interval in proportion to where each falls between the smallest and the largest: music21’s unitNormRange, so [0, 3, 4] is [0, 0.75, 1].

fix_range bounds the interval with a range other than the series’ own. A series of one number answers nought, and so does every number of a series with no spread at all.