/*
 * nm6.java - revised 19 Apr 05 - width 385, height 261
 * @author jack@ord.ca
 * FFSS coefficients for Pulse A and Pulse B 
 *   on an n-segment string clamped at both ends
 */

import java.applet.Applet;
import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

public class nm6 extends Applet 
                 implements ActionListener {
  int kk=0;                                            // Declarations
  String b1s="Pulse A"; Button b1=new Button(b1s);
  String b2s="Pulse B"; Button b2=new Button(b2s);
  Choice ch=new Choice();

  public void init() {
    setBackground(new Color(211, 211, 211));
    ch.setBackground(getBackground());
    ch.addItem("n=48"); ch.addItem("n=96");
    ch.addItem("n=192"); ch.addItem("n=384");
    add(b1); add(b2); add(ch);
    b1.addActionListener(this);
    b2.addActionListener(this);
  }

  public void paint(Graphics g) {
    int n, nm, k, x1, y1, x2, y2;                      // Declarations
    n=48*(int)(Math.pow(2, ch.getSelectedIndex()));
    if (n==48) { nm=n; } else { nm=64; }
    int [] yy=new int[nm+1];
    double [] y=new double[n+1];
    double [] v=new double[n+1];
    double [] b=new double[nm+1];
    double [] d=new double[nm+1];
    double [] w=new double[nm+1];
    double pi, s, z;
    k=0; s=0; z=0; pi=Math.PI;
    g.setColor(Color.black);
    g.drawRect(0, 0, 384, 260);
    if (kk>0) {
      for (int i=3*n/8; i<=5*n/8; i=i+1) {             // Init Pulse A
        z=(i-3*n/8)*pi/(n/8);
        y[i]=40*(1-Math.cos(z));
        v[i]=-40*pi/(n/8)*Math.sin(z);
        if (kk==2) {                                   // Init Pulse B
          v[i]=v[i]*Math.cos(4*z)+y[i]*4*pi/(n/8)*Math.sin(4*z);
          y[i]=y[i]*Math.cos(4*z);
        }
      }
      for (int i=1; i<=nm; i=i+1) {                    // FFSS
        w[i]=2*Math.sin(pi*i/2/n);
        for (int j=1; j<=n-1; j=j+1) {
          b[i]=b[i]+y[j]*2/n*Math.sin(pi*i*j/n);
          d[i]=d[i]+v[j]/w[i]*2/n*Math.sin(pi*i*j/n);
        }
        s=s+b[i]*b[i]+d[i]*d[i];
      }
      g.setColor(Color.red);
      for (int i=1; i<=nm; i=i+1) {                    // Show FFSS coeffts
        yy[i]=260-(int)(1200*(b[i]*b[i]+d[i]*d[i])/s+.5);
        if (yy[i]<1) { yy[i]=1; }
        g.fillRect(6*i-2, yy[i], 5, 260-yy[i]);
      }
      z=0;
      do {
        k=k+1; z=z+b[k]*b[k]+d[k]*d[k];
      } while ((z/s)<.9999);
      g.setColor(Color.black);
      g.drawString("For Nmax  = "+k, 100, 45);
      g.drawString("Percent  = "+(int)(100000*z/s)/1000., 200, 45);
      kk=0;
      g.setColor(Color.blue); x1=0; y1=260;            // Plot dispersion reln
      if (n==48) { nm=288; } else { nm=384; }
      for (int i=n/48; i<=nm; i=i+n/48) {
        x2=i; y2=260-(int)(2.4*n*Math.sin(i*pi/12/n)+.5);
        g.drawLine(x1, y1, x2, y2); x1=x2; y1=y2;
      }
    }
  } 

  public void actionPerformed(ActionEvent e) {         // Buttons
    String tst;
    tst=e.getActionCommand();
    if (b1s.equals(tst)) { kk=1; }                     // Pluck A
    if (b2s.equals(tst)) { kk=2; }                     // Pulse B
    repaint();
  }
}