public class KalmanFilter : Indicator
    {
        private double DeltaK;
        private double Smooth;
        private Series<double> Velocity;
        public double xSlope = 0;
        private const double radToDegrees = 180 / Math.PI;
        private int shallowAngle = 30;
        private int steepAngle = 60;
        private FilterDirection currentDirection;
        public FilterDirection CurrentDirection { get { Update(); return currentDirection; } }
        private FilterDirection directionStatus;
        public enum FilterDirection
        {
            Rising,
            Falling
        }

        protected override void OnStateChange()
        {
            if (State == State.SetDefaults)
            {
                Description = @"Kalman Filter.";
                Name = "KalmanFilter";
                Calculate = Calculate.OnPriceChange;
                IsOverlay = true;
                DisplayInDataBox = false;
                DrawOnPricePanel = true;
                DrawHorizontalGridLines = true;
                DrawVerticalGridLines = true;
                PaintPriceMarkers = false;
                ScaleJustification = NinjaTrader.Gui.Chart.ScaleJustification.Right;
                IsSuspendedWhileInactive = true;

                Gain = 190;
                UseAngle = true;
                fontSize = 12;


                AddPlot(Brushes.Red, "GainLevel");
                Plots[0].Width = 2;
            }
            else if (State == State.Configure)
            {
            }
            else if (State == State.DataLoaded)
            {
                Velocity = new Series<double>(this, MaximumBarsLookBack.Infinite);
            }
        }

        protected override void OnBarUpdate()
        {
            var simpleFont = new SimpleFont("Arial", fontSize) { Size = fontSize, Bold = false };

            if (CurrentBar == 0)
            {
                GainLevel[0] = Input[0];
                Velocity[0] = 0;
                return;
            }

            DeltaK = Input[0] - GainLevel[1];
            Smooth = GainLevel[1] + DeltaK * Math.Sqrt((Gain / 10000) * 2);
            Velocity[0] = Velocity[1] + ((Gain / 10000) * DeltaK);
            GainLevel[0] = Smooth + Velocity[0];

            xSlope = (radToDegrees * (Math.Atan((GainLevel[0] + (GainLevel[1]) / 2) / 1.56 / TickSize)));

            //Draw.TextFixed(this, "Gain", GainLevel[0] + " - Gain Level", TextPosition.BottomRight);
            //Draw.TextFixed(this, "Slope", xSlope + " - Current Slope", TextPosition.BottomLeft);

            Print("\tSlope @ : " + xSlope);

            if (IsRising(GainLevel))
            {
                Draw.TextFixed(this, "Rising", "Is Rising", TextPosition.TopRight);
                directionStatus = FilterDirection.Rising;
            }
            else
            {
                Draw.TextFixed(this, "Rising", "Is Falling", TextPosition.TopRight);
                directionStatus = FilterDirection.Falling;
            }

            currentDirection = directionStatus;

        }

float slope;
Point leftPoint, rightPoint;

leftPoint = new Point(100, 100); // Anchor point 1
rightPoint = new Point(200, 200); // Anchor point 2

// slope = rise over run (rise/run) or (Vertical Y / Time X)
slope = (float)(leftPoint.Y - rightPoint.Y) / (float)(leftPoint.X - rightPoint.X);

angleOfSlope = ( Math.Atan( slope ) * 180 / Math.PI ) *-1;