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 = Math.Sqrt(0.2*0.6);
         BW = 0.6 - 0.2;
         LinearSystems.LowpassToBandstop(z,p,ref k,Wc,BW);  //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
    }