PeakFinderSavitzkyGolay Class

Class PeakFinderSavitzkyGolay uses smooth Savitzky-Golay derivatives to find peaks in data and acts as a collection for the found peaks.

Inheritance Hierarchy

SystemObject
CenterSpace.NMath.CorePeakFinderBase
CenterSpace.NMath.CorePeakFinderSavitzkyGolay

Namespace: CenterSpace.NMath.Core
Assembly: NMath (in NMath.dll) Version: 7.4

Syntax

C++

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public class PeakFinderSavitzkyGolay : PeakFinderBase, 
	ICloneable

Public Class PeakFinderSavitzkyGolay
	Inherits PeakFinderBase
	Implements ICloneable

public ref class PeakFinderSavitzkyGolay : public PeakFinderBase, 
	ICloneable

type PeakFinderSavitzkyGolay = 
    class
        inherit PeakFinderBase
        interface ICloneable
    end

The PeakFinderSavitzkyGolay type exposes the following members.

Constructors

	Name	Description
	PeakFinderSavitzkyGolay(DoubleVector, Int32)	An instance of a Savitkzy-Golay peak finder, using a third degree polynomial.
	PeakFinderSavitzkyGolay(DoubleVector, Int32, Int32)	An instance of a Savitkzy-Golay peak finder. The width of the filter must be less than the length of the data, and the polynomial degree must be less than the filter width.

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Properties

	Name	Description
	AbscissaInterval	Gets\Sets the abscissa interval for the data. This is used to scale the derivatives to the correct units.
	InputData	Gets / Sets the input data. Set nullifies current peak list. (Inherited from PeakFinderBase)
	Item	Gets the extrema via index operator. (Inherited from PeakFinderBase)
	NumberPeaks	Gets the number of peaks found. (Inherited from PeakFinderBase)
	RootFindingTolerance	Gets\Sets the root finders error tolerance. Default is 0.00001;
	SlopeSelectivity	Slope selectivity is between [0,Double.MaxValue] (default = 0.0). Peak finding selectivity increases with larger values. A value of 0 returns all peaks (all smoothed derivative zero crossings).

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Methods

	Name	Description
	ApplySortOrder	Applies the desired sort order on the found peaks. (Inherited from PeakFinderBase)
	Clone	Creates a deep copy of this SavitzkyGolayPeakFinder instance.
	GetAllPeaks	Returns a list of all C# Copy Extrema found. (Inherited from PeakFinderBase)
	LocatePeakIndices	Locates the Indices in the vector preceeding the peak. (Overrides PeakFinderBaseLocatePeakIndices)
	LocatePeaks	Locates the all peak abscissae and their smoothed ordinates in current data set. (Overrides PeakFinderBaseLocatePeaks)
	RetainPeaks(FuncExtrema, Boolean)	Retains C# Copy Extrema in C# Copy this instance that don't satisfy the C# Copy FilterDelegate . (Inherited from PeakFinderBase)
	RetainPeaks(FuncExtrema, Extrema, Extrema, Boolean, Boolean)	Retains C# Copy Extrema in C# Copy this instance that satisfy the C# Copy FilterDelegate , simultaneously for each Extrema, FilterDelegate(extrema[i-1], extrema[i], extrema[i+1]). This allows the filtering of extrema based on the two immediate neighbors. End-point extrema can be dropped at will based on boolean C# Copy DropEdgePeaks . (Inherited from PeakFinderBase)
	SelectPeaks	Obsolete. Deprecated. Selects and returns a list of C# Copy Extrema e that satisfy the C# Copy FilterDelegate . (Inherited from PeakFinderBase)
	SelectPeaksForwardOrder	Selects and returns a list of C# Copy Extrema e that satisfy the C# Copy FilterDelegate . (Inherited from PeakFinderBase)
	SelectPeaksReverseOrder	Selects and returns a list of C# Copy Extrema e that satisfy the C# Copy FilterDelegate . (Inherited from PeakFinderBase)

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Fields

	Name	Description
	findpeaks_	If false, report valleys, otherwise report peaks.
	peakabscissae_	List of the peaks abscissae. (Inherited from PeakFinderBase)
	peakvalues_	List of peaks ordinates. (Inherited from PeakFinderBase)

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Remarks

Typically the degree of the smoothing polynomial is between 3 and 5. The selectivity of the peak finder can be reduced by increasing the SlopeSelectivity. If SlopeSelectivity is set to 0 (default), all found peaks are reported. For proper scaling of the peak abscissa locations, set AbscissaInterval to the data sample interval.

The filter's parameters must satisfied the follow two rules. 1. The filter width must be less than the length of the data. 2. The polynomial degree must be less than the filter width.

Example

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// Build a sinc() function.
double step_size = 0.1;
DoubleVector x = new DoubleVector(5000, 0.01, step_size);
DoubleVector sinc = NMathFunctions.Sin(x) / x;

// Build a peak finder with a width of 6, and 4th degree smoothing polynomial.
PeakFinderSavitzkyGolay pf = new PeakFinderSavitzkyGolay(sinc, 6, 4);
pf.AbscissaInterval = step_size; // Scale abscissa locations.
pf.SlopeSelectivity = 0;         // Return all peaks.
pf.LocatePeaks();                // Locate peaks

// Dump peaks to console.
for (int i = 0; i < pf.NumberPeaks; i++)
  Console.WriteLine("Found peak at = ({0},{1})", pf[i].X, pf[i].Y);

Reference

CenterSpace.NMath.Core Namespace