public static double[] PolynomialFit(Point[] points, int degree)
{
int maxPower = degree * 2 + 2;
double[] b = new double[degree + 1];
double[,] A = new double[degree + 1, degree + 1];
double[,] tiPowerk = new double[points.Length, maxPower];
double[] tPowerSum = new double[maxPower];
double sum, xi;
int i, j;
for (i = 0; i < points.Length; i++)
{
xi = points[i].X;
tiPowerk[i, 0] = sum = 1d;
for (j = 1; j < maxPower; j++)
{
tiPowerk[i, j] = sum *= xi;
}
}
for (i = 0; i < maxPower; i++)
{
sum = 0;
for (j = 0; j < points.Length; j++)
{
sum += tiPowerk[j, i];
}
tPowerSum[i] = sum;
}
for (i = 0; i <= degree; i++)
{
sum = 0;
for (j = 0; j < points.Length; j++)
{
sum += points[j].Y * tiPowerk[j, i];
}
b[i] = sum;
for (j = 0; j <= degree; j++)
{
A[i, j] = tPowerSum[i + j];
}
}
int[] indicies;
LinearEquations.LUDecomposition(A, out indicies);
return(LinearEquations.LUSolve(A, b, indicies));
}
public static double[] PolynomialClosedFit(Point[] points, int degree, int joinDegree)
{
int maxPower = degree * 2 + 2;
double[] b = new double[degree + 1];
double[,] A = new double[degree + 1, degree + 1];
double[,] xiPowerj = new double[points.Length, maxPower];
double[] xPowerSum = new double[maxPower];
double temp, xi;
int i, j;
for (i = 0; i < points.Length; i++)
{
xi = points[i].X;
xiPowerj[i, 0] = temp = 1d;
for (j = 1; j < maxPower; j++)
{
xiPowerj[i, j] = temp *= xi;
}
}
for (i = 0; i < maxPower; i++)
{
temp = 0;
for (j = 0; j < points.Length; j++)
{
temp += xiPowerj[j, i];
}
xPowerSum[i] = temp;
}
for (i = joinDegree; i <= degree; i++)
{
temp = 0;
for (j = 0; j < points.Length; j++)
{
temp += points[j].Y * xiPowerj[j, i];
}
b[i] = temp;
for (j = 0; j <= degree; j++)
{
A[i, j] = xPowerSum[i + j];
}
}
int last = points.Length - 1;
int k;
for (i = 0; i < joinDegree; i++)
{
for (j = 0; j < i; j++)
{
A[i, j] = 0;
}
for (j = i; j <= degree; j++)
{
temp = 1;
for (k = 0; k < i; k++)
{
temp *= (j - k);
}
A[i, j] = temp * (xiPowerj[0, j - i] - xiPowerj[last, j - i]);
}
b[i] = 0;
}
int[] indicies;
LinearEquations.LUDecomposition(A, out indicies);
return(LinearEquations.LUSolve(A, b, indicies));
}
