Chapter - 9: Arrays

For the following set of the point given by (x, y) fit a straight line given by


y = a + bx

where, 

a = y' - bx' and


          n*sigma(y*x) - sigma(x)*sigma(y) 
b =   ---------------------------------
            [n*sigma(x^2) - (sigma(x))^2]


x y
3.0 1.5
4.5 2.0
5.5 3.5
6.5 5.0
7.5 6.0
8.5 7.5
8.0 9.0
9.0 10.5
9.5 12.0
10.0 14.0

#include<stdio.h>
#include<conio.h>

#define n 10

int main()
{
	double set[n][2] = {
		3.0, 1.5,
		4.5, 2.0,
		5.5, 3.5,
		6.5, 5.0,
		7.5, 6.0,
		8.5, 7.5,
		8.0, 9.0,
		9.0, 10.5,
		9.5, 12.0,
		10.0, 14.0
	};
	double help[n], sx = 0, sy = 0, sxy = 0, sx2 = 0, a, b, xbar, ybar;
	int i;

	for (i = 0; i < n; i++)
	{
		sx += set[i][0];
		sy += set[i][1];
		sxy += set[i][0] * set[i][1];
		sx2 += set[i][0] * set[i][0];
	}
	
	xbar = sx / n;
	ybar = sy / n;

	b = (n*sxy - sx*sy) / (n*sx2 - sx*sx);
	a = ybar - b*xbar;

	printf("\nRequired equation is\n\ny = %.2lf + %.2lfx", a, b);
	_getch();
	return 0;
}​

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