Entering Calculation Logic

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Entering Calculation Logic

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The OnBarUpdate() method is called for each incoming tick or on the close of a bar (user defined) when performing real-time calculations and is called on each bar of a data series when re-calculating the indicator. For example, an indicator would be re-calculated when adding it to an existing chart that has existing price data displayed. Therefore, this is the main method called for indicator calculation and we will use this method to enter the script that will do our calculations.

 

Creating the Series<double> Object

This has already been added by the New Indicator wizard, but let's take note of the code added that creates our Series<double>

 

1. Declare a variable ("MySeries" used in this example) of type Series<double> that will hold a Series<double> object within the region "Variables"

2. Create a new Series<double> object and assigning it to the MySeries variable within the OnStateChange() method

 

ns

private Series<double> MySeries;
 
protected override void OnStateChange()
{
if (State == State.SetDefaults)
{
  ...
}
else if (State == State.DataLoaded)
{
  MySeries = new Series<double>(this);
}
}

 

Storing calculations in the DataSeries object
Now that we have our Series<double> object we can store double values into it. For this example we will store a simple Close minus Open calculation.

Enter the following code into the OnBarUpdate() method:

 

ns

// Calculate the range of the current bar and set the value
MySeries[0] = Close[0] - Open[0];

 

The value of a Series<T> object will be aligned with the current bar. This means that all Series<T> objects will be synced with the CurrentBar index. It allows you to store a double value that corresponds with every bar.

 

Using Series<T> values
With our new Series<double> object we can continue with further calculations easily. We can now use our Series<double> object as input to an indicator method such as SMA or instead of always writing Close[0] - Open[0] we can substitute our Series<double> object instead as per the example below.

 

To plot our final calculation we will store the calculation in our plot called 'MyPlot.' In the OnBarUpdate() method add the following code snippet:

 

ns

// Add the bar's range to the SMA value
MyPlot[0] = SMA(SMAPeriod)[0] + MySeries[0];

 
Here we assign the SMA + Series<double> value to the property that represents the plot data using the "=" assignment operator. We have just finished coding our CustomSeries example. The class code in your editor should look identical to the below. You are now ready to compile the indicator and configure it on a chart.

 

ns

public class CustomSeries : Indicator
{
  private Series<double> MySeries;
 
  protected override void OnStateChange()
  {
    if (State == State.SetDefaults)
    {
        Description                           = @"Stores intermediary calculations without the use of plots";
        Name                                 = "CustomSeries";
        Calculate                             = Calculate.OnBarClose;
        IsOverlay                             = false;
        DisplayInDataBox                     = true;
        DrawOnPricePanel                     = true;
        DrawHorizontalGridLines               = true;
        DrawVerticalGridLines                 = true;
        PaintPriceMarkers                     = true;
        ScaleJustification                   = NinjaTrader.Gui.Chart.ScaleJustification.Right;
        //Disable this property if your indicator requires custom values that cumulate with each new market data event.
        //See Help Guide for additional information.
        IsSuspendedWhileInactive             = true;
        SMAPeriod                             = 5;
        AddPlot(Brushes.Orange, "MyPlot");
    }
    else if (State == State.Configure)
    {
    }
    else if (State == State.DataLoaded)
    {            
        MySeries = new Series<double>(this);
    }
  }
 
  protected override void OnBarUpdate()
  {
    // Calculate the range of the current bar and set the value
    MySeries[0] = Close[0] - Open[0];
     
    // Add the bar's range to the SMA value
    MyPlot[0] = SMA(SMAPeriod)[0] + MySeries[0];
  }
 
  #region Properties
  [NinjaScriptProperty]
  [Range(1, int.MaxValue)]
  [Display(Name="SMAPeriod", Description="Simple Moving Average Period", Order=1, GroupName="Parameters")]
  public int SMAPeriod
  { get; set; }
 
  [Browsable(false)]
  [XmlIgnore]
  public Series<double> MyPlot
  {
    get { return Values[0]; }
  }
  #endregion
 
}