Mean, Variance, and Standard Deviation Methods

MeanVarStDev.cs

/// <summary>
/// Calculates the mean of an array of values
/// </summary>
/// <param name="v">the array of values to calculate their mean</param>
/// <returns>The mean of the array of values</returns>
public static double Mean(double[] v)
{
    double sum = 0.0;

    for (int i = 0; i < v.Length; i++)
    {
        sum += v[i];
    }

    return sum / v.Length;
}

/// <summary>
/// Calculates the variance of an array of values
/// </summary>
/// <param name="v">the array of values to calculate their variance</param>
/// <returns>The variance of the array of values</returns>
public static double Variance(double[] v)
{
    double mean = Mean(v);
    double sum = 0.0;

    for (int i = 0; i < v.Length; i++)
    {
        sum += (v[i] - mean) * (v[i] - mean);
    }

    int denom = v.Length - 1;
    if (v.Length <= 1)
        denom = v.Length;

    return sum / denom;
}

/// <summary>
/// Calculates the standard deviation of an array of values
/// </summary>
/// <param name="v">the array of values to calculate their standard deviation</param>
/// <returns>The standard deviation of the array of values</returns>
public static double StDev(double[] v)
{
    return Math.Sqrt(Variance(v));
}