spline

#include "stdafx.h" #include <iostream> #include "math.h" using namespace std; const int N = 5; const double A = 1; const double B = 3; const double eps = pow(10, -6); void run(double* Below, double* Diag1, double* Above, double* Right, int n) { n--; // тк начинаем с х0 а не с х1 Above[0] /= Diag1[0]; Right[0] /= Diag1[0]; for (int i = 1; i < n; i++) { Above[i] /= Diag1[i] - Below[i] * Above[i - 1]; Right[i] = (Right[i] - Below[i] * Right[i - 1]) / (Diag1[i] - Below[i] * Above[i - 1]); } Right[n] = (Right[n] - Below[n] * Right[n - 1]) / (Diag1[n] - Below[n] * Above[n - 1]); for (int i = n; i-- > 0;) { Right[i] -= Above[i] * Right[i + 1]; } } double spl(double* h, double* x, double* y, double* gamma, double var, int i) //значение сплайна в данной точке { double S; S = y[i] * (x[i + 1] - var) / h[i + 1]; S += y[i + 1] * (var - x[i]) / h[i + 1]; S += gamma[i] * (pow(x[i + 1] - var, 3) - h[i + 1] * h[i + 1] * (x[i + 1] - var)) / (6 * h[i + 1]); S += gamma[i + 1] * (pow(var - x[i], 3) - h[i + 1] * h[i + 1] * (var - x[i])) / (6 * h[i + 1]); return S; } int main() { int n = 4; double a[4] = { 0, -1, -1, -1 }; double b[4] = { 4, 4, 4, 4 }; double c[4] = { -1, -1, -1, 0 }; double d[4] = { 5, 5, 10, 23 }; // results { 2, 3, 5, 7 } run(a, b, c, d, n); for (int i = 0; i < n; i++) { cout << d[i] << endl; } cout << endl << "n= " << n << endl << "n is not changed hooray !!"; double x_in[N], y_in[N]; double h[N - 1]; double gamma[N]; gamma[0] = A; gamma[N] = B; //ввод данных интерполяции, вычисление шагов for (int i = 0; i < N; i++) { cin >> x_in[i]; } for (int i = 0; i < N - 1; i++) { h[i] = x_in[i+1] - x_in[i]; } double Diag[N - 1], F[N-1], BelowDiag[N - 1], AboveDiag[N - 1]; for (int i = 0; i < N - 1; i++) { Diag[i] = 2 * (h[i] + h[i + 1]); F[i] = 6 * ((y_in[i + 1] - y_in[i]) / h[i + 1] - (y_in[i] - y_in[i - 1]) / h[i]); } for (int i = 1; i < N - 1; i++) { BelowDiag[i] = h[i + 1]; } BelowDiag[0] = 0; for (int i = 0; i < N; i++) { AboveDiag[i] = h[i + 1]; } AboveDiag[N] = 0; //вывод run(BelowDiag, Diag, AboveDiag, F, N - 1); /* for (int i = 1; i < N; i++) { cout << "h[" << i << "] " << h[i] << endl; } for (int i = 1; i < N; i++) { cout << "D[" << i << "] " << Diag[i] << endl; cout << "F[" << i << "] " << F[i] << endl; } */ system("pause"); return 0; }