138 lines
3.4 KiB
C++
138 lines
3.4 KiB
C++
#include <iostream>
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#include <fstream>
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#include <sstream>
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#include <vector>
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#include <iomanip>
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#include <cmath>
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using namespace std;
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class Interpolacja
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{
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public:
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void readFromFile(string filename)
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{
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string str;
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fstream file(filename);
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if (!file)
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{
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cerr << "Nie udalo sie otworzyc pliku o nazwie: " << filename << "\n";
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exit(EXIT_FAILURE);
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}
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while (getline(file, str))
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{
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istringstream iss(str);
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if (iss >> a >> b)
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{
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x.push_back(a);
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y.push_back(b);
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}
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}
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liczba_wezlow = x.size();
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if (liczba_wezlow < 2)
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{
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cerr << "Za malo danych do interpolacji.\n";
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exit(EXIT_FAILURE);
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}
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h = x[1] - x[0];
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file.close();
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}
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void oblicz()
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{
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rowne_odstepy = true;
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float pierwszy_odstep = x[1] - x[0];
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// Sprawdzenie czy odstępy x są takie same
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for (int i = 2; i < liczba_wezlow; i++)
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{
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if (std::abs((x[i] - x[i - 1]) - pierwszy_odstep) > 1e-6)
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{
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rowne_odstepy = false;
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break;
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}
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}
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if (rowne_odstepy)
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{
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// Newton
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tablica_roznic.assign(liczba_wezlow, vector<float>(liczba_wezlow, 0));
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for (int i = 0; i < liczba_wezlow; i++)
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{
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tablica_roznic[i][0] = y[i];
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}
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for (int j = 1; j < liczba_wezlow; j++)
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{
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for (int i = 0; i < liczba_wezlow - j; i++)
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{
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tablica_roznic[i][j] = (tablica_roznic[i + 1][j - 1] - tablica_roznic[i][j - 1]);
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}
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}
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suma = tablica_roznic[0][0];
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for (int i = 1; i < liczba_wezlow; i++)
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{
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czynnik = tablica_roznic[0][i];
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for (int j = 0; j < i; j++)
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{
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czynnik *= (x[j] - x[0]);
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}
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suma += czynnik;
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}
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}
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else
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{
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// Lagrange
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suma = 0;
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for (int i = 0; i < liczba_wezlow; i++)
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{
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float L = 1;
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for (int j = 0; j < liczba_wezlow; j++)
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{
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if (i != j)
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{
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L *= (x[j] - x[0]) / (x[j] - x[i]);
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}
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}
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suma += L * y[i];
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}
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}
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}
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void wyswietl_tabela()
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{
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if(rowne_odstepy) {
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// nagłowki
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cout << setw(5) << "i" << setw(10) << "x" << setw(10) << "y";
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for (int j = 1; j < liczba_wezlow; ++j)
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cout << setw(10) << "Δ^" + to_string(j);
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cout << endl;
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// wartości
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for (int i = 0; i < liczba_wezlow; i++)
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{
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cout << setw(5) << i << setw(10) << x[i];
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for (int j = 0; j < liczba_wezlow - i; j++)
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{
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cout << setw(10) << tablica_roznic[i][j];
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}
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cout << endl;
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}
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}
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cout << "Interpolowany wynik: " << suma << endl;
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}
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private:
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float a, b, h, suma, czynnik;
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int liczba_wezlow;
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bool rowne_odstepy;
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vector<float> x, y;
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vector<vector<float> > tablica_roznic;
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};
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