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 k,Wc,BW;
       double FS = 2;
       int Order = 5; //design a fifth order filter.

       IIRFilters.EllipticAnalog(Order,0.2,40,z,p,out k);  //design analog protype
       Wc = 0.7;
       LinearSystems.LowpassToLowpass(z,p,ref k,Wc);  //frequency transformation in s-domain
       LinearSystems.ZeroPoleToTransferFun(num,den,z,p,k);
    //Define the frequency grid (logarithmic)
       FreqFr.Length = 1000;
       SignalUtils.LogRamp(FreqFr,-1,1); //between 0.1 (=10^(-1)) and 10 (=10^1) rad/sec
       SignalUtils.FrequencyResponseS(num,den,FreqFr,Response,0); //Laplace
       TeeChart.DrawIt(Response,"Frequency response",false); //Y axis linear, X axis logarithmic
  }