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December 3, 2017 02:46
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C++ source code to interporate with Lagrange method.
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/********************************************* | |
* ラグランジュ補間 | |
*********************************************/ | |
#include <iostream> // for cout | |
#include <stdio.h> // for printf() | |
using namespace std; | |
/* | |
* 計算クラス | |
*/ | |
class Calc | |
{ | |
// 各種変数 | |
int n; // あらかじめ与える点の数 | |
double s, p; // 総和, 総積 | |
int i, j; // LOOP インデックス | |
double t; // LOOP インデックス | |
public: | |
// 計算 | |
void calc(); | |
// ラグランジュ補間 | |
double interpolateLagrange(double x[], double y[], int n, double t); | |
}; | |
/* | |
* 計算 | |
*/ | |
void Calc::calc() | |
{ | |
// あらかじめ与える点 | |
double x[] = {0.0, 2.0, 3.0, 5.0, 8.0}; | |
double y[] = {0.8, 3.2, 2.8, 4.5, 1.9}; | |
// 点の数 | |
n = sizeof(x) / sizeof(x[0]); | |
// 結果出力 | |
printf(" x y\n"); | |
for (t = x[0]; t <= x[n - 1]; t += .5) | |
printf("%7.2f%7.2f\n", t, interpolateLagrange(x, y, n, t)); | |
} | |
/* | |
* ラグランジュ補間 | |
*/ | |
double Calc::interpolateLagrange(double x[], double y[], int n, double t) | |
{ | |
// 総和初期化 | |
s = 0.0; | |
// 総和 | |
for (i = 0; i < n; i++) { | |
p = y[i]; | |
// 総積 | |
for (j = 0; j < n; j++) { | |
if (i != j) | |
p *= (t - x[j]) / (x[i] - x[j]); | |
} | |
s += p; | |
} | |
return s; | |
} | |
/* | |
* メイン処理 | |
*/ | |
int main() | |
{ | |
try | |
{ | |
// 計算クラスインスタンス化 | |
Calc objCalc; | |
// ラグランジュ補間計算 | |
objCalc.calc(); | |
} | |
catch (...) { | |
cout << "例外発生!" << endl; | |
return -1; | |
} | |
// 正常終了 | |
return 0; | |
} |
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