Contoh regresi linier dan regresi kuadratik pada C++
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#include <iostream> | |
#include <iomanip> | |
#include <cmath> | |
using namespace std; | |
// ================== | |
// CONTOH DATA (X, Y) | |
// ================== | |
const int n = 6; | |
float data[n][2] = { | |
{ 0, 2.1 }, | |
{ 1, 7.7 }, | |
{ 2, 13.6 }, | |
{ 3, 27.2 }, | |
{ 4, 40.9 }, | |
{ 5, 61.1 } | |
}; | |
// only support 3x3 for now | |
void printGaussMatrix (float X[3][3], float Y[3]) { | |
for (int i = 0; i < 3; ++i) { | |
for (int j = 0; j < 3; ++j) { | |
cout.width(10); | |
cout << right << X[i][j]; | |
} | |
cout << " | "; | |
cout.width(10); | |
cout << right << Y[i] << '\n'; | |
} | |
} | |
int main () { | |
cout.precision(2); | |
cout.setf(ios::fixed); | |
float sumX = 0, sumX2 = 0, sumX3 = 0, sumX4 = 0; | |
float sumY = 0, sumXY = 0, sumX2Y = 0; | |
for (int i = 0; i < n; ++i) { | |
sumX += data[i][0]; | |
sumX2 += pow(data[i][0], 2); | |
sumX3 += pow(data[i][0], 3); | |
sumX4 += pow(data[i][0], 4); | |
sumY += data[i][1]; | |
sumXY += data[i][0] * data[i][1]; | |
sumX2Y += pow(data[i][0], 2) * data[i][1]; | |
} | |
float X[3][3] = { | |
n, sumX, sumX2, | |
sumX, sumX2, sumX3, | |
sumX2, sumX3, sumX4 | |
}; | |
float Y[3] = { | |
sumY, | |
sumXY, | |
sumX2Y | |
}; | |
cout << "Iter# " << 0 << ":" << endl; | |
printGaussMatrix(X, Y); | |
cout << endl; | |
// ELIMINASI GAUSS | |
const int XROWS = 3; | |
const int XCOLS = 3; | |
const int YROWS = 3; | |
for (int i = 0; i < XCOLS - 1; ++i) { | |
for (int j = i + 1; j < XROWS; ++j) { | |
float d = X[j][i] / X[i][i]; | |
for (int k = 0; k < XCOLS; ++k) { | |
X[j][k] = X[j][k] - X[i][k] * d; | |
} | |
Y[j] = Y[j] - Y[i] * d; | |
cout << "Iter# " | |
<< i + 1 | |
<< "," | |
<< j + 1 | |
<< " pembagi: " | |
<< d | |
<< endl; | |
printGaussMatrix(X, Y); | |
cout << endl; | |
} | |
} | |
// SUBSTITUSI MUNDUR | |
float A[3]; // i => 0, 1, 2 | |
float s; | |
for (int i = 2; i >= 0; i--) { | |
s = 0; | |
if (i < 2) { | |
for (int j = i + 1; j <= 2; ++j) { | |
s += X[i][j] * A[j]; | |
} | |
} | |
A[i] = (Y[i] - s) / X[i][i]; | |
cout << "A" | |
<< i | |
<< " = " | |
<< A[i] | |
<< endl; | |
} | |
float totalErrorY = 0; | |
for (int i = 0; i < n; ++i) { | |
float prediction = A[0] | |
+ A[1] * data[i][0] | |
+ A[2] * pow(data[i][0], 2); | |
totalErrorY += abs(data[i][1] - prediction); | |
} | |
float meanAbsErrorY = totalErrorY / n; | |
cout << "y = " | |
<< A[0] | |
<< " + " | |
<< A[1] | |
<< "x" | |
<< " + " | |
<< A[2] | |
<< "x2" | |
<< ", err ~" | |
<< meanAbsErrorY | |
<< endl; | |
return 0; | |
} |
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#include <iostream> | |
#include <cmath> | |
using namespace std; | |
// ======================== | |
// DATA PERTUMBUHAN TANAMAN | |
// ======================== | |
const int n = 7; | |
int data[n][2] = { | |
{ 1, 2 }, | |
{ 3, 5 }, | |
{ 7, 12 }, | |
{ 9, 14 }, | |
{ 11, 15 }, | |
{ 20, 20 }, | |
{ 22, 25 } | |
}; | |
int main () { | |
int sumXY = 0, sumX = 0, sumY = 0, sumX2 = 0; | |
for (int i = 0; i < n; ++i) { | |
sumXY += data[i][0] * data[i][1]; | |
sumX += data[i][0]; | |
sumY += data[i][1]; | |
sumX2 += pow(data[i][0], 2); | |
} | |
float avgY = sumY / n; | |
float avgX = sumX / n; | |
float a1 = (n * sumXY - sumX * sumY) | |
/ (n * sumX2 - pow(sumX, 2)); | |
float a0 = avgY - a1 * avgX; | |
float totalErrorY = 0; | |
for (int i = 0; i < n; ++i) { | |
float prediction = a0 + a1 * data[i][0]; | |
totalErrorY += abs(data[i][1] - prediction); | |
} | |
float meanAbsErrorY = totalErrorY / n; | |
cout << "y = " | |
<< a0 | |
<< " + " | |
<< a1 | |
<< "x" | |
<< ", err ~" | |
<< meanAbsErrorY | |
<< endl; | |
return 0; | |
} |
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