/// <summary>
/// Calculates the a term (slope) of the linear regression function (y = a*x + b)
/// given the Y and X values.
/// </summary>
/// <param name="y">Y values</param>
/// <param name="x">X values</param>
/// <returns>The a term of y = a*x + b</returns>
public static double ATerm2(Statistics y, Statistics x)
{
try
{
return Covariance(y, x) / (Math.Pow(x.StdDev(), 2));
}
catch (Exception)
{
return double.NaN;
}
}
/// <summary>
/// Calculates the covariance between two sets of numbers.
/// </summary>
/// <param name="s1">First set of numbers</param>
/// <param name="s2">Second set of numbers</param>
/// <returns></returns>
public static double Covariance(Statistics s1, Statistics s2)
{
try
{
if (s1.Length != s2.Length)
return double.NaN;
int len = s1.Length;
double sumMul = 0;
for (int i = 0; i < len; i++)
sumMul += (s1._list[i]*s2._list[i]);
return (sumMul - len*s1.Mean()*s2.Mean())/(len - 1);
}
catch (Exception)
{
return double.NaN;
}
}
/// <summary>
/// Calculates the slope (a term) of the linear regression function (y = a*x + b)
/// given the Y and X values.
/// </summary>
/// <param name="y">Y values</param>
/// <param name="x">X values</param>
/// <returns>The slope</returns>
public static double Slope(Statistics y, Statistics x)
{
return ATerm2(y, x);
}
/// <summary>
/// Calculates the slope (a term) of the linear regression function (y = a*x + b)
/// using the current set of numbers as Y values and another set
/// as X values.
/// </summary>
/// <param name="x">X values</param>
/// <returns>The slope</returns>
public double Slope(Statistics x)
{
return ATerm2(x);
}
/// <summary>
/// Calculates the a term (slope) of the linear regression function (y = a*x + b)
/// using the current set of numbers as Y values and another set
/// as X values.
/// </summary>
/// <param name="x">X values</param>
/// <returns>The a term of y = a*x + b</returns>
public double ATerm2(Statistics x)
{
return ATerm2(this, x);
}
