using System;

using MathNet.Numerics;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Calculating linear regression");

        List<(double, DateTime)> collatedEgfrMeasurements = new List<(double, DateTime)>()

        {

            //Oldest egfr first

            (88, DateTime.Parse("2023-03-02T00:00:00")),

            (80, DateTime.Parse("2023-09-25T00:00:00")),

            (91, DateTime.Parse("2024-04-20T00:00:00")),

            (94, DateTime.Parse("2024-06-25T00:00:00")),

            (91, DateTime.Parse("2024-08-21T00:00:00")),

            (84, DateTime.Parse("2024-11-26T00:00:00")),

        };

        //collatedEgfrMeasurements will have all egfr measurements in the last 2 years from DateTime.Now

        double[] egfrMeasurements = collatedEgfrMeasurements.Select(x => x.Item1).ToArray();

        List<DateTime> egfrDates = collatedEgfrMeasurements.Select(x => x.Item2).ToList();

​

        //Gets the number of days since two years ago (from DateTime.Now) and converts to a decimal year

        DateTime twentyFourMonthsAgo = DateTime.Now.AddYears(-2);

        double[] elapsedDatesInYears = egfrDates.Select(x => Convert.ToDouble(((x - twentyFourMonthsAgo).TotalDays)/365)).ToArray();

​

        //Do a linear regression to calculate the slope

        (double A, double B) regression = Fit.Line(elapsedDatesInYears, egfrMeasurements);

        double intercept = regression.A;

        double slope = regression.B;

        Console.WriteLine("Intercept is: " + intercept);

        Console.WriteLine("Slope is: " + slope);

    }

}