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December 22, 2017 04:58
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C++ source code to solve approximate equation with least squares method.
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/********************************************* | |
* 最小二乗法 * | |
*********************************************/ | |
#include <iostream> // for cout | |
#include <stdio.h> // for printf() | |
#define N 7 // データ数 | |
#define M 5 // 予測曲線の次数 | |
using namespace std; | |
/* | |
* 計算クラス | |
*/ | |
class Calc | |
{ | |
// 各種変数 | |
double a[M + 1][M + 2], s[2 * M + 1], t[M + 1]; | |
int i, j, k; | |
double p, d, px; | |
public: | |
Calc(); // コンストラクタ | |
void calcLeastSquaresMethod(); // 最小二乗法 | |
double ipow(double, int); // べき乗計算 | |
}; | |
/* | |
* コンストラクタ | |
*/ | |
Calc::Calc() | |
{ | |
// s, t 初期化 | |
for (i = 0; i <= 2 * M; i++) | |
s[i] = 0; | |
for (i = 0; i <= M; i++) | |
t[i] = 0; | |
} | |
/* | |
* 最小二乗法 | |
*/ | |
void Calc::calcLeastSquaresMethod() | |
{ | |
// 測定データ | |
static double x[] = {-3, -2, -1, 0, 1, 2, 3}; | |
static double y[] = { 5, -2, -3, -1, 1, 4, 5}; | |
// s[], t[] 計算 | |
for (i = 0; i < N; i++) { | |
for (j = 0; j <= 2 * M; j++) | |
s[j] += ipow(x[i], j); | |
for (j = 0; j <= M; j++) | |
t[j] += ipow(x[i], j) * y[i]; | |
} | |
// a[][] に s[], t[] 代入 | |
for (i = 0; i <= M; i++) { | |
for (j = 0; j <= M; j++) | |
a[i][j] = s[i + j]; | |
a[i][M + 1] = t[i]; | |
} | |
// 掃き出し | |
for (k = 0; k <= M; k++) { | |
p = a[k][k]; | |
for (j = k; j <= M + 1; j++) | |
a[k][j] /= p; | |
for (i = 0; i <= M; i++) { | |
if (i != k) { | |
d = a[i][k]; | |
for (j = k; j <= M + 1; j++) | |
a[i][j] -= d * a[k][j]; | |
} | |
} | |
} | |
// y 値計算&結果出力 | |
for (k = 0; k <= M; k++) | |
printf("a%d = %10.6f\n", k, a[k][M + 1]); | |
printf(" x y\n"); | |
for (px = -3; px <= 3; px += .5) { | |
p = 0; | |
for (k = 0; k <= M; k++) | |
p += a[k][M + 1] * ipow(px, k); | |
printf("%5.1f%5.1f\n", px, p); | |
} | |
} | |
/* | |
* べき乗計算 | |
*/ | |
double Calc::ipow(double p, int n) | |
{ | |
int k; | |
double s = 1; | |
for (k = 1; k <= n; k++) | |
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; | |
// 最小二乗法 | |
objCalc.calcLeastSquaresMethod(); | |
} | |
catch (...) { | |
cout << "例外発生!" << endl; | |
return -1; | |
} | |
// 正常終了 | |
return 0; | |
} |
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