/*
 * rctrps.java - revised 22 Apr 05 - width 421, height 346
 *   tests 4 different capacitors by analyzing R-C transients
 *   with nominal 20 ms time constants
 * @author jackord@kw.igs.net
 * revised for consistency with Liberty Basic version with eps option
 */

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

public class rctrps extends Applet
                    implements ActionListener {
  int xz=400; int yz=320; int np=32; int kk=0;         // Declarations
  double ym=4096;
  double la, lb, lsy;
  String b1s = "C1"; Button b1 = new Button(b1s);
  String b2s = "C2"; Button b2 = new Button(b2s);
  String b3s = "C3"; Button b3 = new Button(b3s);
  String b4s = "C4"; Button b4 = new Button(b4s);
  String b5s = "fit"; Button b5 = new Button(b5s);
  TextField tx1=new TextField(20);
  TextField tx2=new TextField(20);
  char URLSeparator='/';
  String fs;
  double[] x=new double[33];
  double[] y=new double[33];
  double[] z=new double[33];

  public void init() {
    setBackground(new Color(211, 211, 211));
    tx1.setBackground(getBackground());
    tx2.setBackground(getBackground());
    add(b1); add(b2); add(b3); add(b4); add(b5);
    add(tx1); add(tx2);
    b1.addActionListener(this);
    b2.addActionListener(this);
    b3.addActionListener(this);
    b4.addActionListener(this);
    b5.addActionListener(this);
  }

  public void pin(Graphics g) {
    b1.setBounds(10, 0, 30, 20);                         // Screen layout
    b2.setBounds(45, 0, 30, 20);
    b3.setBounds(80, 0, 30, 20);
    b4.setBounds(115, 0, 30, 20);
    b5.setBounds(150, 0, 30, 20);
    tx1.setBounds(190, 0, 105, 20);
    tx2.setBounds(305, 0, 105, 20);
    tx1.setText("Time Constant"); tx2.setText("Deviation");
    g.setColor(Color.black);                           // Draw grid
    for (int i=10; i<=xz+10; i=i+40) {
      g.drawLine(i, 25, i, yz+25);
    }
    for (int i=25; i<=yz+25; i=i+40) {
      g.drawLine(10, i, xz+10, i);
    }
  }

  public void paint(Graphics g) {                      // Main program
    int test=0; int y1, y2;
    double t, dt, yy;
    double h=0;
    pin(g);
    if (kk>0) {
      for (int i=1; i<=np; i=i+1) {                    // Plot raw data
        g.setColor(Color.green);                      
        g.fillArc(4*(int)(x[i])+5, (int)(yz*(1-y[i]/ym)+.5)+20, 11, 11, 0, 360);
        g.setColor(Color.black);                      
        g.drawArc(4*(int)(x[i])+5, (int)(yz*(1-y[i]/ym)+.5)+20, 10, 10, 0, 360);
      }
    }
    if (kk==2) {                                       // Vary t for best fit
      t=x[np]/Math.log(np); dt=t/4;
      lsq(t); h=lsy;
      while (test==0) {
        t=t+dt; lsq(t);
        if (lsy>h) {
          dt=-dt/2;
          if (Math.abs(dt)<(t/100000)) {
            test=1; lsy=h; t=t+2*dt;
          }
        }
        h=lsy;
      }
      lsq(t);
      for (int i=1; i<=np; i=i+1) {                    // Plot fitted data
        g.setColor(Color.blue);                        
        g.fillArc((int)(z[i]*xz+.5)+5, (int)(yz*(1-y[i]/ym)+.5)+20, 11, 11, 0, 360);
        g.setColor(Color.black);                        
        g.drawArc((int)(z[i]*xz+.5)+5, (int)(yz*(1-y[i]/ym)+.5)+20, 10, 10, 0, 360);
      }
      tx1.setText("t ="+(float)t); tx2.setText("d ="+(float)lsy);
      g.setColor(Color.red);
      y1=25+(int)(yz*(1-(la+lb)/ym)+.5);               // Fitted line
      g.drawLine(10, 25+(int)(yz*(1-lb/ym)+.5), 410, y1);
      for (int i=1; i<=np-1; i=i+1) {                  // Fitted curve
        y2=25+(int)(yz*(1-(la*Math.exp(-x[i+1]/t)+lb)/ym)+.5);
        g.drawLine(10+4*(int)(x[i]), y1, 10+4*(int)(x[i+1]), y2); y1=y2;
      }
      for (int i=1; i<=np; i=i+1) {                    // Scatter plot
        yy=y[i]-la*z[i]-lb;
        if (lsy>3) {                                   // Divide by 20 for C4
          yy=yy/20;
        }
        yy=185-40*yy;
        g.setColor(Color.red);
        g.fillArc((int)(z[i]*xz+.5)+5, (int)(yy+.5)-5, 11, 11, 0, 360);
        g.setColor(Color.black);
        g.drawArc((int)(z[i]*xz+.5)+5, (int)(yy+.5)-5, 10, 10, 0, 360);
      }
      kk=0;
    }
  }

  public void lsq(double t) {                          // Fit y=la*x+lb
    double l0, l1, l2, l3, l4, ls;
    for (int i=1; i<=np; i=i+1) {                      // Convert to exp
      z[i]=Math.exp(-x[i]/t);
    }
    l1=0; l2=0; l3=0; l4=0; ls=0;                      // Start analysis from
    for (int i=2; i<=np; i=i+1) {                      //   2nd point
      l1=l1+z[i]; l4=l4+y[i];
    }
    l1=l1/(np-1); l4=l4/(np-1);
    for (int i=2; i<=np; i=i+1) {
      l0=z[i]-l1; l2=l2+l0*(y[i]-l4); l3=l3+l0*l0;
    }
    la=l2/l3; lb=-la*l1+l4;
    for (int i=2; i<=np; i=i+1) {
      l0=y[i]-la*z[i]-lb; ls=ls+l0*l0;
    }
    lsy=Math.sqrt(ls/(np-3));
  }

  public void actionPerformed(ActionEvent e) {
    String tst;
    tst=e.getActionCommand();
    if (b1s.equals(tst)) {
      kk=1;
      x[1]=0;   y[1]=4086;  x[2]=1;   y[2]=3843;  x[3]=2;   y[3]=3651;
      x[4]=3;   y[4]=3468;  x[5]=4;   y[5]=3294;  x[6]=5;   y[6]=3129;
      x[7]=6;   y[7]=2972;  x[8]=7;   y[8]=2823;  x[9]=8;   y[9]=2682;
      x[10]=9;  y[10]=2548; x[11]=10; y[11]=2420; x[12]=11; y[12]=2299;
      x[13]=12; y[13]=2184; x[14]=13; y[14]=2075; x[15]=14; y[15]=1971;
      x[16]=15; y[16]=1873; x[17]=16; y[17]=1779; x[18]=17; y[18]=1690;
      x[19]=18; y[19]=1606; x[20]=19; y[20]=1526; x[21]=20; y[21]=1450;
      x[22]=21; y[22]=1377; x[23]=23; y[23]=1243; x[24]=25; y[24]=1123;
      x[25]=27; y[25]=1014; x[26]=30; y[26]=870;  x[27]=33; y[27]=747;
      x[28]=37; y[28]=610;  x[29]=41; y[29]=498;  x[30]=47; y[30]=368;
      x[31]=55; y[31]=247;  x[32]=69; y[32]=125;
    }
    if (b2s.equals(tst)) {
      kk=1;
      x[1]=0;   y[1]=4086;  x[2]=1;   y[2]=3842;  x[3]=2;   y[3]=3650;
      x[4]=3;   y[4]=3468;  x[5]=4;   y[5]=3295;  x[6]=5;   y[6]=3131;
      x[7]=6;   y[7]=2975;  x[8]=7;   y[8]=2827;  x[9]=8;   y[9]=2686;
      x[10]=9;  y[10]=2552; x[11]=10; y[11]=2425; x[12]=11; y[12]=2305;
      x[13]=12; y[13]=2190; x[14]=13; y[14]=2081; x[15]=14; y[15]=1978;
      x[16]=15; y[16]=1880; x[17]=16; y[17]=1787; x[18]=17; y[18]=1698;
      x[19]=18; y[19]=1614; x[20]=19; y[20]=1534; x[21]=20; y[21]=1458;
      x[22]=21; y[22]=1385; x[23]=23; y[23]=1252; x[24]=25; y[24]=1131;
      x[25]=27; y[25]=1022; x[26]=30; y[26]=878;  x[27]=33; y[27]=755;
      x[28]=37; y[28]=617;  x[29]=41; y[29]=505;  x[30]=47; y[30]=374;
      x[31]=55; y[31]=252;  x[32]=70; y[32]=123;
    }
    if (b3s.equals(tst)) {
      kk=1;
      x[1]=0;   y[1]=4086;  x[2]=1;   y[2]=3870;  x[3]=2;   y[3]=3698;
      x[4]=3;   y[4]=3536;  x[5]=4;   y[5]=3381;  x[6]=5;   y[6]=3233;
      x[7]=6;   y[7]=3092;  x[8]=7;   y[8]=2957;  x[9]=8;   y[9]=2829;
      x[10]=9;  y[10]=2706; x[11]=10; y[11]=2588; x[12]=11; y[12]=2476;
      x[13]=12; y[13]=2368; x[14]=13; y[14]=2266; x[15]=14; y[15]=2168;
      x[16]=15; y[16]=2074; x[17]=16; y[17]=1985; x[18]=17; y[18]=1899;
      x[19]=19; y[19]=1739; x[20]=21; y[20]=1593; x[21]=22; y[21]=1524;
      x[22]=24; y[22]=1397; x[23]=27; y[23]=1226; x[24]=29; y[24]=1124;
      x[25]=32; y[25]=988;  x[26]=35; y[26]=868;  x[27]=38; y[27]=764;
      x[28]=43; y[28]=618;  x[29]=48; y[29]=501;  x[30]=55; y[30]=375;
      x[31]=65; y[31]=250;  x[32]=83; y[32]=124;
    }
    if (b4s.equals(tst)) {
      kk=1;
      x[1]=0;   y[1]=4086;  x[2]=1;   y[2]=3875;  x[3]=2;   y[3]=3709;
      x[4]=3;   y[4]=3562;  x[5]=4;   y[5]=3428;  x[6]=5;   y[6]=3304;
      x[7]=6;   y[7]=3188;  x[8]=7;   y[8]=3078;  x[9]=8;   y[9]=2974;
      x[10]=9;  y[10]=2873; x[11]=10; y[11]=2776; x[12]=11; y[12]=2681;
      x[13]=13; y[13]=2494; x[14]=14; y[14]=2399; x[15]=15; y[15]=2302;
      x[16]=17; y[16]=2103; x[17]=18; y[17]=2003; x[18]=19; y[18]=1904;
      x[19]=21; y[19]=1721; x[20]=22; y[20]=1640; x[21]=24; y[21]=1497;
      x[22]=26; y[22]=1376; x[23]=28; y[23]=1271; x[24]=31; y[24]=1135;
      x[25]=34; y[25]=1018; x[26]=38; y[26]=886;  x[27]=43; y[27]=749;
      x[28]=48; y[28]=635;  x[29]=55; y[29]=506;  x[30]=64; y[30]=379;
      x[31]=77; y[31]=251;  x[32]=100;y[32]=125;
    }
    if (b5s.equals(tst)) { if (kk==1) { kk=2; } else { kk=0; } }
    repaint();
  }
}