VB DWT Example

Imports System
Imports System.Globalization
Imports System.Threading
Imports System.Text

Imports CenterSpace.NMath.Core


Namespace CenterSpace.NMath.Examples.VisualBasic

  A .NET example in Visual Basic showing how to use the Discrete Wavelet Transform (DWT) classes.
  Module DWTExample

    Sub Main()

      This section shows to use various configuration settings. All of these settings can
      also be set via configuration file or by environment variable. More on this at: 
      http://www.centerspace.net/blog/nmath/nmath-configuration/

      For NMath to continue to work after your evaluation period, you must set your license 
      key. You will receive a license key after purchase. 
      More here:
      http://www.centerspace.net/blog/nmath/setting-the-nmath-license-key/
      NMathConfiguration.LicenseKey = "<key>"

      This will start a log file that you can use to ensure that your configuration is 
      correct. This can be especially useful
      for deployment. Please turn this off when you are convinced everything is 
      working. If you arent sure, please send the resulting log file to 
      support@centerspace.net. Please note that this directory can be relative or absolute.
      NMathConfiguration.LogLocation = "<dir>"
      
      NMath loads native, optimized libraries at runtime. There is a one-time cost to 
      doing so. To take control of when this happens, use Init(). If your program calls 
      Init() successfully, then your configuration is definitely correct.
      NMathConfiguration.Init()
	  

      Console.WriteLine()

      DWT of a signal using the Harr wavelet.

      Do a simple DWT on a signal
      Dim Data As New DoubleVector(12, New RandGenNormal(0.0, 2.0))

      Choose wavelet
      Dim WaveletInstance As New DoubleWavelet(Wavelet.Wavelets.Harr)

      Build DWT object
      Dim DWT As New DoubleDWT(WaveletInstance)

      Decompose signal with DWT
      Dim Approx() As Double
      Dim Details() As Double
      DWT.DWT(Data.DataBlock.Data, Approx, Details)

      Rebuild the signal
      Dim Signal() As Double = DWT.IDWT(Approx, Details)

      Print results
      Console.WriteLine()
      Console.WriteLine("A DWT signal decomposition and reconstruction example using the Harr wavelet.")
      Console.WriteLine(String.Format("Original Signal: {0}", Data.ToString("#.##")))
      Console.WriteLine(String.Format("DWT Approximation: {0}", New DoubleVector(Approx).ToString("#.##")))
      Console.WriteLine(String.Format("DWT Details: {0}", New DoubleVector(Details).ToString("#.##")))
      Console.WriteLine(String.Format("IDWT Reconstructed signal: {0}", New DoubleVector(Signal).ToString("#.##")))

      DWT using a Daubeachies wavelet, then thresholding, and finally reconstucting the signal.

      An example to filter a signal using the DWT.
      Build random signal data
      Data = New DoubleVector(26, New RandGenNormal(1.0, 1.0))

      Choose wavelet
      WaveletInstance = New DoubleWavelet(Wavelet.Wavelets.D2)

      Build DWT object
      DWT = New DoubleDWT(Data.DataBlock.Data, WaveletInstance)

      Decompose signal with DWT to level 5
      DWT.Decompose(3)

      Find Universal threshold
      Dim LambdaU As Double = DWT.ComputeThreshold(DoubleDWT.ThresholdMethod.Universal, 1)

      Threshold all detail levels with lambdaU
      DWT.ThresholdAllLevels(DoubleDWT.ThresholdPolicy.Soft, New Double() {LambdaU, LambdaU, LambdaU, LambdaU, LambdaU})

      Rebuild signal to level 2
      Dim ReconstructedData2() As Double = DWT.Reconstruct(2)

      Rebuild the signal to level 1 - the original (filtered) signal.
      Dim ReconstructedData1() As Double = DWT.Reconstruct()

      Print results
      Console.WriteLine()
      Console.WriteLine("A DWT signal thresholding and reconstruction example using a Daubeachies wavelet.")
      Console.WriteLine(String.Format("Original Signal: "))
      Console.WriteLine(" {0}", Data.ToString("#.##"))
      Console.WriteLine()
      Console.WriteLine(String.Format("IDWT Reconstructed signal: "))
      Console.WriteLine(" {0}", New DoubleVector(ReconstructedData1).ToString("#.##"))

      Console.WriteLine()
      Console.WriteLine("Finished. Press Enter Key.")
      Console.Read()

    End Sub
  End Module
End Namespace