/**
  *  A Quint instance is a set of five (x,y) equally spaced points.
  *  A parabola is fitted to the derivative of the middle three.
  *  Glen Cowan, RHUL Physics, June 2004
  */

import java.math.*;

public class Quint {

// constructors

  public Quint(double dx, double[] y){
    for (int i=0; i<5; i++){
      this.dx = dx;
      this.x[i] = (double)(i-2) * dx;        // define x[2] = 0
      this.y[i] = y[i];
      this.sigma[i] = 1;
    }
  }

  public Quint(double dx, double[] y, double[] sigma){
    this(dx,y);
    for (int i=0; i<5; i++){
      this.sigma[i] = sigma[i];
    } 
  }

  public Quint(double[] x, double[] y){
    for (int i=0; i<5; i++){
      this.x[i] = x[i];
      this.y[i] = y[i];
      this.sigma[i] = 1;
    }
    this.dx = x[1] - x[0];
  }

  public Quint(double[] x, double[] y, double[] sigma){
    this(x,y);
    for (int i=0; i<5; i++){
      this.sigma[i] = sigma[i];
    }
  }

// public methods

  public double[] getX() { return x; }
  public double[] getY() { return y; }
  public double[] getSigma() { return sigma; }
  public void setX(double[] x) {
    for(int i=0; i<5; i++){ this.x[i] = x[i]; }
  }
  public void setY(double[] y) {
    for(int i=0; i<5; i++){ this.y[i] = y[i]; }
  }
  public void setSigma(double[] sigma) {
    for(int i=0; i<5; i++){ this.sigma[i] = sigma[i]; }
  }

  public double mu(){ 
    double a = 2*y[2] - y[0] - y[4];
    double b = y[0] - 2*y[1] + 2*y[3] - y[4];
    double muVal = x[2] - 0.5*dx*a/b;
    return muVal;
  }

  public double sigmaMu() {
    double a = 2*y[2] - y[0] - y[4];
    double b = y[0] - 2*y[1] + 2*y[3] - y[4];
    double a2 = Math.pow(a,2);
    double b2 = Math.pow(b,2);
    double apb2 = Math.pow(a+b,2);
    double amb2 = Math.pow(a-b,2);
    double[] s2 = new double[5];
    for (int i=0; i<5; i++){ s2[i] = Math.pow(sigma[i],2); }
    double c = Math.pow(0.5*dx/b2, 2);
    double varMu = c * (apb2*s2[0] + 2*a2*s2[1] + 2*b2*s2[2] +
                        2*a2*s2[3] + amb2*s2[4]);
    double sigVal = Math.sqrt(varMu);
    return sigVal;
  }

  public double deriv(int i) {
    double d;
    if ( i <= 0 || i >= 4 ) {
      d = 0; }
    else {
      d = (y[i+1] - y[i-1])/(2*dx);
    }
    return d;
  }

  public double peakDeriv() {
    double xmp = mu();
    double c1 = (deriv(3) - deriv(1))/(2*dx);
    double c2 = (deriv(3) + deriv(1) - 2*deriv(2))/(2*Math.pow(dx,2));
    double ymp = deriv(2) + c1*(xmp - x[2]) + c2*Math.pow((xmp-x[2]),2);
    return ymp;
  }

  public boolean goodPeak(){

    boolean allPos = true;
    boolean allNeg = true;
    for (int i=1; i<4; i++){
      if ( deriv(i) > 0 ) { allNeg = false; }
      if ( deriv(i) < 0 ) { allPos = false; }
    }

    int edgePixel = 1;
    double maxDeriv = Math.abs(deriv(1));
    for (int i=1; i<4; i++){
      if (Math.abs(deriv(i)) > maxDeriv) {
	  maxDeriv = Math.abs(deriv(i));
        edgePixel = i;
      }
    }

    boolean gP = (allPos || allNeg) && edgePixel == 2;
    return gP;

  }

// private data fields

  double[] x = new double[5];
  double[] y = new double[5];
  double[] sigma = new double[5];
  double dx;

}