Momentum in NinjaTrader — NinjaScript (C#) Source

Momentum is the simplest NinjaScript oscillator there is — one subtraction against a bar Period ago. See the explainer for the concept.

What you’ll need

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

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 AlgoGenMomentum : Indicator
    {
        protected override void OnStateChange()
        {
            if (State == State.SetDefaults)
            {
                Name        = "AlgoGen Momentum";
                Description = "Momentum (difference form)";
                Period      = 10;
                IsOverlay   = false;

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

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

            Value[0] = Close[0] - Close[Period];    // difference form
            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 Momentum to a chart; the histogram 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.
• Difference vs ratio. This is the difference form (around 0); for the ratio form (around 100) use 100.0 * Close[0] / Close[Period].
• No fixed levels. Colour by sign (vs zero) for a clean regime read; judge extremes relative to recent range, or add a signal-line SMA for crossovers.
• Signal line. Store Momentum in a Series<double> and plot SMA(momSeries, 3) for smoother crossover signals than the raw line.
• Trend filter. In a strategy, gate the zero-cross on a longer average — Close[0] > SMA(200)[0] — to avoid the range-bound whipsaw that plagues any unfiltered momentum tool.
• Built-in. Momentum(Period)[0] exists in NinjaTrader (difference form); the hand-rolled version is for learning and for exposing the ratio option.

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