numeric-statistics 0.1.1

Numeric Statistics: functions for min, max, average, variance, standard deviation, and more to come.
Documentation 
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use super::variance;

/// Calculate statistical standard deviation for values.
///
/// Return NaN if the values are empty.
///
pub fn standard_deviation<T: AsRef<[f64]>>(values: T) -> f64 {
    standard_deviation_with_variance(variance(&values))
}

/// Calculate statistical standard deviation for values, 
/// given a pre-calculated variance value.
///
/// Return NaN if the values are empty.
///
pub fn standard_deviation_with_variance(variance: f64) -> f64 {
    variance.sqrt()
}

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn test_empty() {
        let x: &[f64] = &[];
        assert!(standard_deviation(x).is_nan());
    }

    #[test]
    fn test_nan() {
        let x: &[f64] = &[f64::NAN];
        assert!(standard_deviation(x).is_nan());
    }

    #[test]
    fn test_value() {
        let x: &[f64] = &[1.0];
        assert_eq_float!(standard_deviation(x), 0.0);
    }

    #[test]
    fn test_values_ascending() {
        let x = &[1.0, 2.0, 4.0];
        assert_eq_float!(standard_deviation(x), 1.5275252316519465);
    }

    #[test]
    fn test_values_ascending_and_nans() {
        let x = &[1.0, f64::NAN, 2.0, f64::NAN, 4.0];
        assert_eq_float!(standard_deviation(x), 1.5275252316519465);
    }

}