Linear regression model update method

LinearRegressionModel.Update.cs

public void Update(double x, double y)
{
    count++;
    sumX    += x;
    sumY    += y;
    sumXY   += x * y;
    sumXX   += x * x;
    sumYY   += y * y;

    double meanX    = sumX / count;
    double meanY    = sumY / count;
    double meanXY   = sumXY / count;
    double meanXX   = sumXX / count;

    beta = (meanXY - meanX * meanY) / (meanXX - meanX * meanX);
    alpha = meanY - beta * meanX;
}