ZigZag Linear Regression Channels

//#reference: SwingZigZag.algo

using System;
using cAlgo.API;
using cAlgo.API.Internals;
using cAlgo.API.Indicators;
using cAlgo.Indicators;

namespace cAlgo
{
    [Indicator(IsOverlay = true, TimeZone = TimeZones.UTC, AccessRights = AccessRights.None)]
    public class ZZ_LRC : Indicator
    {
        [Parameter(DefaultValue = 10)]
        public int Period { get; set; }

        private IndicatorDataSeries zzSeries;
        private SwingZigZag zz;

        protected override void Initialize()
        {
            zzSeries = CreateDataSeries();
            zz = Indicators.GetIndicator<SwingZigZag>(Period);
        }

        public override void Calculate(int index)
        {
            if (!IsLastBar)
                return;

            int x1 = -1;
            int x2 = -1;

            for (int i = 1; i < MarketSeries.Open.Count; i++)
            {
                zzSeries[i] = zz.ZigZag[i];

                if (!double.IsNaN(zzSeries[i]))
                {
                    if (x1 == -1 || x2 == -1)
                    {
                        x1 = i;
                        x2 = i;
                    }
                    else
                    {
                        x1 = x2 - 1;
                        x2 = i;
                    }

                    var Source = MarketSeries.Close;
                    int period = x2 - x1 + 1;

                    double sumX = 0;
                    double sumX2 = 0;
                    double sumY = 0;
                    double sumXY = 0;

                    for (int count = x1; count <= x2; count++)
                    {
                        sumX += count;
                        sumX2 += count * count;
                        sumY += Source[count];
                        sumXY += Source[count] * count;
                    }

                    double divisor = (period * sumX2 - sumX * sumX);
                    double slope = (period * sumXY - sumX * sumY) / divisor;
                    double intercept = (sumY - slope * sumX) / period;

                    double deviation = 0;

                    for (int count = x1; count <= x2; count++)
                    {
                        double regression = slope * count + intercept;
                        deviation = Math.Max(Math.Abs(Source[count] - regression), deviation);
                    }


                    double y1 = slope * x1 + intercept;
                    double y2 = slope * x2 + intercept;


                    ChartObjects.DrawLine("Middle" + x1, x1, y1, x2, y2, Colors.Black, 0.5, LineStyle.Lines);
                    ChartObjects.DrawLine("Upper" + x1, x1, y1 + deviation, x2, y2 + deviation, Colors.Black, 1, LineStyle.Solid);
                    ChartObjects.DrawLine("Lower" + x1, x1, y1 - deviation, x2, y2 - deviation, Colors.Black, 1, LineStyle.Solid);
                }
            }
        }
    }
}