Fibonacci Retracement in NinjaTrader — NinjaScript (C#) Source

NinjaTrader has a manual Fibonacci drawing tool, but scripting it lets you auto-draw levels from a rule-based swing — the objective, testable approach (see the explainer).

What you’ll need

• NinjaTrader 8
• New → NinjaScript Editor → Indicators → New Indicator, name it AlgoGenFibonacci

The source

#region Using declarations
using System;
using System.Windows.Media;
using NinjaTrader.NinjaScript;
using NinjaTrader.NinjaScript.Indicators;
#endregion

namespace NinjaTrader.NinjaScript.Indicators
{
    public class AlgoGenFibonacci : Indicator
    {
        private static readonly double[] Ratios =
            { 0.0, 0.236, 0.382, 0.5, 0.618, 0.786, 1.0 };

        protected override void OnStateChange()
        {
            if (State == State.SetDefaults)
            {
                Name        = "AlgoGen Fibonacci";
                Description = "Auto Fibonacci retracement";
                Lookback    = 90;
                IsOverlay   = true;
            }
        }

        protected override void OnBarUpdate()
        {
            if (CurrentBar < Lookback) return;

            double swingHigh = High[HighestBar(High, Lookback)];
            double swingLow  = Low[LowestBar(Low, Lookback)];
            double diff = swingHigh - swingLow;

            foreach (double r in Ratios)
            {
                double y = swingLow + r * diff;
                bool emph = r == 0.5 || r == 0.618;
                Draw.HorizontalLine(this, "fib_" + r, y,
                    emph ? Brushes.OrangeRed : Brushes.Gray);
                Draw.Text(this, "fiblbl_" + r, (r * 100).ToString("0.#") + "%",
                    0, y, Brushes.Gray);
            }
        }

        #region Properties
        [NinjaScriptProperty][System.ComponentModel.DataAnnotations.Range(2, int.MaxValue)]
        [System.ComponentModel.Display(Name = "Lookback", GroupName = "Parameters", Order = 0)]
        public int Lookback { get; set; }
        #endregion
    }
}

Compile & apply

1. Press F5 to compile.
2. Add AlgoGen Fibonacci to a chart; it draws the retracement levels of the last Lookback bars’ swing, matching the output chart.

Gotchas

• HighestBar/LowestBar return the bars-ago offset of the extreme; index High[...]/Low[...] with it to get the swing prices — the rule-based swing.
• Reuse tag names. Passing the same "fib_" + r tag each bar updates the line rather than stacking new ones, so the levels move cleanly as the swing changes.
• 50% is a convention, not a Fibonacci ratio — included because Dow Theory favored the half-retracement.
• Golden-zone region. To shade the 38.2–61.8% zone, use Draw.Rectangle between those two prices, or check Close[0] against them for a signal:

double gLow  = swingLow + 0.382 * diff;
double gHigh = swingLow + 0.618 * diff;
if (Close[0] >= gLow && Close[0] <= gHigh)
    Draw.Dot(this, "inzone" + CurrentBar, false, 0, Low[0] - TickSize, Brushes.Orange);

• Extensions for targets. Add 1.272 and 1.618 to the Ratios array to draw extension levels beyond 100% for profit targets.

That’s the five-language set: Python, MQL5, Pine Script, EasyLanguage, and this one. Now test whether the levels hold in AlgoGen.

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This post is educational, not financial advice. Indicators describe the past; they don’t predict the future. Backtest anything before you risk real money on it.