Example 1

    uses MtxExpr, Math387, MtxVec, SignalUtils, MtxVecTee, MtxVecEdit, IirFilters,
         LinearSystems;

    procedure TForm1.Button1Click(Sender: TObject);
    var z,p, num,den, FreqFr,Response: Vector;
        Order: integer;
        k,Bw,Wc: TSample;
        WcArray: TSampleArray; //modified 3dB frequency
    begin
        SetLength(WcArray,2);
        Order := ButterOrder([0.2,0.3,0.6,0.7],0.2,50,ftBandstop,WcArray);
        ButterFilter(Order,WcArray,ftBandstop,false,num,den);

      // Alternative 1. Specify the order and the 3 dB frequencies explicitely:
      //
      //     ButterFilter(5,[0.2,0.7],ftBandstop,false,num,den);


      // Alternative 2. Specifying the 3 dB frequencies explicitely
      // will result in 3 dB ripple (and not 0.2 as requested) in the passband,
      // but one coulde always move the 3 dB frequencies a little:
      //
      //     ButterFilter(5,[0.22,0.68],ftBandstop,false,num,den);

      // Alternative 3. Specifying the order explicitely
      // will not ensure 50 dB attenuation in the edges of the stopband,
      // but one can increase filter order:
      //
      //     ButterFilter(10,[0.22,0.68],ftBandstop,false,num,den);

        FrequencyResponse(num,den,Response,64);
        DrawIt(Response);
    end;

    #include "MtxVecCPP.h" //MtxVecCPP.cpp must be included in the project
    #include "MtxVecEdit.hpp"
    #include "MtxVecTee.hpp"
    #include "SignalUtils.hpp"
    #include "IirFilters.hpp"
    #include "LinearSystems.hpp"

    void __fastcall TForm41::BitBtn1Click(TObject *Sender)
    {
      Vector z,p, num,den, FreqFr, Response, WcArray;
      int	Order;
      double k,Wc,Bw;

      WcArray->Size(2);
      Order = ButterOrder(OPENARRAY(double,(0.2,0.3,0.6,0.7)),0.2,50,ftBandStop,WcArray->PValues1D(0),WcArray->Length-1);
      ButterFilter(Order,WcArray->PValues1D(0),WcArray->Length-1,ftBandStop,false,num,den);

      // Alternative 1. Specify the order and the 3 dB frequencies explicitely:
      //
      //     ButterFilter(5,OPENARRAY(double,(0.2,0.7)),ftBandStop,false,num,den);


      // Alternative 2. Specifying the 3 dB frequencies explicitely
      // will result in 3 dB ripple (and not 0.2 as requested) in the passband,
      // but one coulde always move the 3 dB frequencies a little:
      //
      //     ButterFilter(5,OPENARRAY(double,(0.22,0.68)),ftBandStop,false,num,den);

      // Alternative 3. Specifying the order explicitely
      // will not ensure 50 dB attenuation in the edges of the stopband,
      // but one can increase filter order:
      //
      //     ButterFilter(10,OPENARRAY(double,(0.22,0.68)),ftBandStop,false,num,den);

      FrequencyResponse(num,den,Response,64);
      DrawIt(Response);
    }

  using Dew.Math;
  using Dew.Math.Editors;
  using Dew.Math.Units;
  using Dew.Signal;
  using Dew.Signal.Units;
  using Dew.Math.Tee;
  using Dew.Signal.Tee;

  private void button1_Click(object sender, EventArgs e)
  {
      Vector z = new Vector(0);
      Vector p = new Vector(0);
      Vector num = new Vector(0);
      Vector den = new Vector(0);
      Vector Response = new Vector(0);
      Vector FreqFr = new Vector(0);
      double[] WcArray = new double[2];
      int Order; //design a fifth order filter.

      Order = IIRFilters.ButterOrder(new double[4] { 0.2, 0.3, 0.6, 0.7 }, 0.2, 50, TFilterType.ftBandStop, ref WcArray, true);  //design analog protype
      IIRFilters.ButterFilter(Order, WcArray, TFilterType.ftBandStop, false, num, den, TIirFrequencyTransform.ftStateSpaceAnalog);

      // Alternative 1. Specify the order and the 3 dB frequencies explicitely:
      //
      //     IIRFilters.ButterFilter(5, new double[2] {0.2,0.7}, TFilterType.ftBandStop,false,num,den,TIirFrequencyTransform.ftStateSpaceAnalog);


      // Alternative 2. Specifying the 3 dB frequencies explicitely
      // will result in 3 dB ripple (and not 0.2 as requested) in the passband,
      // but one coulde always move the 3 dB frequencies a little:
      //
      //     IIRFilters.ButterFilter(5, new double[2] { 0.22, 0.68 }, TFilterType.ftBandStop, false, num, den, TIirFrequencyTransform.ftStateSpaceAnalog);

      // Alternative 3. Specifying the order explicitely
      // will not ensure 50 dB attenuation in the edges of the stopband,
      // but one can increase filter order:
      //
      //     IIRFilters.ButterFilter(10, new double[2] { 0.22, 0.68 }, TFilterType.ftBandStop, false, num, den, TIirFrequencyTransform.ftStateSpaceAnalog);
            
      SignalUtils.FrequencyResponse(num, den, Response, 32, false, TSignalWindowType.wtRectangular, 0);
      TeeChart.DrawIt(Response, "Frequency response", false);
  }