How to calculate the Linest of given numbers

Linest function in excel returns a table of statistics for a straight line that best fits a data set.

The C# code for getting the linest of numbers is given below:

public static double CalculateLinest(double[] y, double[] x)

{

   double linest = 0;

   if (y.Length == x.Length)

   {

      double avgY = y.Average();

      double avgX = x.Average();

      double[] dividend = new double[y.Length];

      double[] divisor = new double[y.Length];

      for (int i = 0; i < y.Length; i++)

      {

         dividend[i] = (x[i] - avgX) * (y[i] - avgY);

         divisor[i] = Math.Pow((x[i] - avgX), 2);

      }

      linest = dividend.Sum() / divisor.Sum();

   }

   return linest;

}