ROC in NinjaTrader — NinjaScript (C#) Source

The Rate of Change is about the simplest NinjaScript oscillator you can write — one comparison to a bar Period ago. See the explainer for the concept.

What you’ll need

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

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 AlgoGenROC : Indicator
    {
        protected override void OnStateChange()
        {
            if (State == State.SetDefaults)
            {
                Name        = "AlgoGen ROC";
                Description = "Rate of Change (percent)";
                Period      = 12;
                IsOverlay   = false;

                AddPlot(new Stroke(Brushes.DodgerBlue, 2), PlotStyle.Line, "ROC");
                AddLine(Brushes.Gray, 0, "Zero");
            }
        }

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

            double past = Close[Period];
            Value[0] = past != 0 ? 100.0 * (Close[0] - past) / past : 0.0;
            PlotBrushes[0][0] = Value[0] >= 0 ? Brushes.MediumSeaGreen : Brushes.IndianRed;
        }

        #region Properties
        [NinjaScriptProperty]
        [System.ComponentModel.DataAnnotations.Range(1, int.MaxValue)]
        [System.ComponentModel.Display(Name = "Period", GroupName = "Parameters", Order = 0)]
        public int Period { get; set; }
        #endregion
    }
}

Compile & apply

1. Press F5 to compile.
2. Add AlgoGen ROC to a chart; the oscillator draws in its own panel around a zero line, matching the output chart.

Gotchas

• Close[Period] is the close Period bars ago; the CurrentBar < Period guard ensures it exists before you divide.
• Divide-by-zero guard. past != 0 protects the ratio.
• Percentage vs difference. This is the percent-change ROC; for the absolute Momentum, just plot Close[0] - Close[Period]. Colour by sign (compare to zero) to make the regime pop.
• Add a signal line. Store ROC in a Series<double> and plot SMA(rocSeries, 9) for crossover signals — the raw line is jumpy on its own.
• Adaptive extremes. Since ROC has no fixed bounds, flag stretches with a rolling z-score ((Value[0] - SMA(rocSeries,100)[0]) / StdDev(rocSeries,100)[0]) rather than a hard threshold that won’t travel across instruments.

That’s the five-language set: Python, MQL5, Pine Script, EasyLanguage, and this one. Now test an ROC rule 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.