Hi @Minu476, thank you for opening this issue!

Re-stating the suggestion, Bollinger bands typically report mean ± 2*SD, but an option should be added to allow customizing the 2 coefficient

I like the idea! I'll add that into the next release. Relevant code is here:

ScottPlot/src/ScottPlot4/ScottPlot/Plottable/FinancePlot.cs

Lines 278 to 294 in 5a823d4

    
           /// <summary> 
        
           /// Return Bollinger bands (mean +/- 2*SD) for the OHLC closing prices. 
        
           /// The returned xs are times in OATime units. 
        
           /// The returned xs and ys arrays will be the length of the OHLC data minus N (points). 
        
           /// </summary> 
        
           /// <param name="N">each returned value represents the average of N points</param> 
        
           /// <returns>times, averages, and both Bollinger bands for the OHLC closing prices</returns> 
        
           public (double[] xs, double[] sma, double[] lower, double[] upper) GetBollingerBands(int N) 
        
           { 
        
               if (N >= OHLCs.Count) 
        
                   throw new ArgumentException("can not analyze more points than are available in the OHLCs"); 
        
               List<IOHLC> sortedOHLCs = GetSortedOHLCs(); 
        
               double[] xs = sortedOHLCs.Skip(N).Select(x => x.DateTime.ToOADate()).ToArray(); 
        
               (var sma, var lower, var upper) = Statistics.Finance.Bollinger(sortedOHLCs.ToArray(), N); 
        
               return (xs, sma, lower, upper); 
        
           }

I notice that the core functions that calculate the Bollinger bands already accept sdCoeff as an optional argument, so the solution here is to add a BollingerSD property to the FinancePlot to allow it to be customized.

EDIT: The best solution is the one you proposed

I'll add this in today and include it in the next release 👍

	/// <summary>
	/// Return Bollinger bands (mean +/- 2*SD) for the OHLC closing prices.
	/// The returned xs are times in OATime units.
	/// The returned xs and ys arrays will be the length of the OHLC data minus N (points).
	/// </summary>
	/// <param name="N">each returned value represents the average of N points</param>
	/// <returns>times, averages, and both Bollinger bands for the OHLC closing prices</returns>
	public (double[] xs, double[] sma, double[] lower, double[] upper) GetBollingerBands(int N)
	{
	if (N >= OHLCs.Count)
	throw new ArgumentException("can not analyze more points than are available in the OHLCs");

	List<IOHLC> sortedOHLCs = GetSortedOHLCs();
	double[] xs = sortedOHLCs.Skip(N).Select(x => x.DateTime.ToOADate()).ToArray();
	(var sma, var lower, var upper) = Statistics.Finance.Bollinger(sortedOHLCs.ToArray(), N);
	return (xs, sma, lower, upper);
	}

FinancePlot.GetBollingerBands(): add sdCoeff argument #2594

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FinancePlot.GetBollingerBands(): add `sdCoeff` argument #2594