Function gain_curve 

pub fn gain_curve(
    scores: &[f64],
    labels: &[bool],
) -> Result<Vec<GainPoint>, StatsError>

Compute the cumulative gain / lift curve from predicted scores and true binary labels. Points are ordered by descending score and always start at fraction == 0, gain == 0.

Errors

• StatsError::LengthMismatch if the inputs differ in length.
• StatsError::EmptyInput if empty.
• StatsError::NoPositiveLabels if there are no positives (gain undefined).