public class Spline

{

  private int n;

  private double[] x;

  private double[] y;

  private double[][] S;



  int size()

  {

	return n;

  }

  Spline()

  {

	n=0;

	x=new double[1];

	y=new double[1];

	S=new double[4][0];

  }



  void AgregarPunto(double px,double py)

  {

	int i;

	n++;

	double[] tempx=new double[n];

	double[] tempy=new double[n];

	if(n==1)

	{

	 tempx[0]=px;

	 tempy[0]=py;

	}

	else

	{

		for(i=0;i<n-1&&px>x[i];i++)

		{

		 tempx[i]=x[i];

		 tempy[i]=y[i];

		}

		if(px==x[i])

		  return;

		tempx[i]=px;

		tempy[i]=py;

		for(i=i+1;i<n;i++)

		{

		 tempx[i]=x[i-1];

		 tempy[i]=y[i-1];

		}

	}

	x=tempx;

	y=tempy;



  }

  void Interpolar()

  {

	double h[]=new double[n];
	double l[]=new double[n];
	double u[]=new double[n];
	double z[]=new double[n];
	double a[]=new double[n];

	S=new double[4][n-1];

	n=n-1;



	int i,j;

	for(i=0;i<=n;i++) S[0][i]=y[i];

	for(i=0;i<=n-1;i++) h[i] = x[i+1] - x[i];

	for(i=1;i<=n-1;i++) a[i] = (3.0/h[i]*(S[0][i+1]-S[0][i])) - (3.0/h[i-1]*(S[0][i]-S[0][i-1]));



	l[0] = 1; u[0] = 0; z[0] = 0;



	for(i=1;i<=n-1;i++){

		l[i] = 2*(x[i+1]-x[i-1]) - h[i-1]*u[i-1];

		u[i] = h[i]/l[i];

		z[i] = (a[i] - h[i-1]*z[i-1])/l[i];

	}



	l[n] = 1; z[n] = 0; S[2][n] = 0;



	for(j=n-1;j>=0;j--){

		S[2][j] = z[j] - u[j]*S[2][j+1];

		S[1][j] = (S[0][j+1]-S[0][j])/h[j] - h[j]*(S[2][j+1]+2.0*S[2][j])/3.0;

		S[3][j] = (S[2][j+1] - S[2][j])/(3.0*h[j]);

		}

  n++;

  }

  double[][] DevolverFuncion(int m)

  {

	 double h=(x[n]-x[0])/m;

	 double[][] xy=new double[m][2];

	 int cont=0;

	 for(int i=0;i<n-1;n++)

		for(double px=x[i];px<x[i+1];px+=h)

		 {

		  xy[cont][0]=px;

		  xy[cont][1]=0;

		  for(int k=0;k<4;k++)

			 xy[cont][1]+=S[i][k]*Math.pow(px-x[i],k);//Esto debe ser equivalente a pow()

		  cont++;

		 }

	 return xy;

  }

}