tindi 0.8.0

Technical Stock Chart Indicators
Documentation 
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/// # Standard Deviation
/// The standard deviation is a measure of how spread out numbers are.
/// It is calculated as the square root of the average of the squared differences
/// from the mean.
///
/// ## Example
/// ```no_run
/// let data = vec![
///     53.73, 53.87, 53.85, 53.88, 54.08, 54.14, 54.5, 54.3, 54.4, 54.16,
/// ];
/// let result = standard_deviation(&data);
/// let expect = 0.257227;
///
/// assert_eq!(result, expect);
/// ```

pub fn standard_deviation(data: &[f32]) -> f32 {
    let length = data.len() as f32;

    if length < 1.0 {
        return 0.0;
    }

    let mean = data.iter().sum::<f32>() / length;
    let variance = data.iter().map(|value| (value - mean).powi(2)).sum::<f32>() / (length - 1.0);
    variance.sqrt()
}

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

    #[test]
    fn test_standard_deviation_results() {
        let data = vec![
            53.73, 53.87, 53.85, 53.88, 54.08, 54.14, 54.5, 54.3, 54.4, 54.16,
        ];
        let result = standard_deviation(&data);
        dbg!(&result);
        let expect = 0.257227;

        assert_eq!(result, expect);
    }
}