# Numerical Methods: Parabolic curve fitting using C

Source Code:

#include<stdio.h>
#include<math.h>
int main(){
float xy[20][20], matrix[3][4], ratio, a;
float sum_x = 0, sum_y = 0, sum_x2 = 0, sum_x3 = 0, sum_x4 = 0, sum_xy = 0, sum_x2y = 0;
int i, j , k, n;
printf("Enter no of data: ");
scanf("%d", &n);
printf("Enter the data: \n");
for(i = 0; i < 2; i++){
for(j = 0; j < n; j++){
scanf("%f", &xy[i][j]);
}
}
for(i = 0; i < n; i++){
sum_x += xy[0][i];
sum_y += xy[1][i];
sum_x2 += pow(xy[0][i], 2);
sum_x3 += pow(xy[0][i], 3);
sum_x4 += pow(xy[0][i], 4);
sum_xy += xy[0][i]*xy[1][i];
sum_x2y += pow(xy[0][i], 2) * xy[1][i];
}
matrix[0][0] = n;
matrix[0][1] = sum_x;
matrix[0][2] = sum_x2;
matrix[0][3] = sum_y;
matrix[1][0] = sum_x;
matrix[1][1] = sum_x2;
matrix[1][2] = sum_x3;
matrix[1][3] = sum_xy;
matrix[2][0] = sum_x2;
matrix[2][1] = sum_x3;
matrix[2][2] = sum_x4;
matrix[2][3] = sum_x2y;
for(i = 0; i < 3; i++){
for(j = 0; j < 3; j++){
if(i!=j){
ratio = matrix[j][i]/matrix[i][i];
for(k = 0; k < 4; k++){
matrix[j][k] -= ratio * matrix[i][k];
}
}
}
}
for(i = 0; i < 3; i++){
a = matrix[i][i];
for(j = 0; j < 4; j++){
matrix[i][j] /= a;
}
}
for(i = 0; i < 3; i++){
printf("\n%c => %.2f", 97+i, matrix[i][3]);
}
}
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### 1 Response

1. doesn't work