#include "interpolation.h"
Interpolation::Interpolation()
{
}
double Interpolation::Lagrange(int N, vector<double>& X, vector<double>& Y, double x)
{
double result = 0;
for (int i = 0; i < N; i++) {
double temp = Y[i];
for (int j = 0; j < N; j++) {
if (i != j) {
temp = temp * (x - X[j]);
temp = temp / (X[i] - X[j]);
}
}
result += temp;
}
return result;
}
double Interpolation::ChaShang(int n, vector<double>& X, vector<double>& Y)
{
double f = 0;
double temp = 0;
for (int i = 0; i < n + 1; i++) {
temp = Y[i];
for (int j = 0; j < n + 1; j++)
if (i != j)
temp /= (X[i] - X[j]);
f += temp;
}
return f;
}
double Interpolation::Newton(double x, vector<double>& X, vector<double>& Y)
{
double result = 0;
for (unsigned int i = 0; i < X.size(); i++) {
double temp = 1;
double f = ChaShang(i, X, Y);
for (unsigned int j = 0; j < i; j++) {
temp = temp * (x - X[j]);
}
result += f * temp;
}
return result;
}
