# C Program for Linear Regression Method

This C program implements Linear Regression Method using Least Square Method to find linear equation of best fit.

In this program we first read n data points from user and then we implement linear regression using C programming language as follow:

## C Program: Linear Regression (Fitting y = a+bx)

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

#define S 50

int main()
{
int n, i;
float x[S], y[S], sumX=0, sumX2=0, sumY=0, sumXY=0, a, b;
clrscr();
/* Input */
printf("How many data points?\n");
scanf("%d", &n);
printf("Enter data:\n");
for(i=1;i<=n;i++)
{
printf("x[%d]=",i);
scanf("%f", &x[i]);
printf("y[%d]=",i);
scanf("%f", &y[i]);
}
/* Calculating Required Sum */
for(i=1;i<=n;i++)
{
sumX = sumX + x[i];
sumX2 = sumX2 + x[i]*x[i];
sumY = sumY + y[i];
sumXY = sumXY + x[i]*y[i];
}
/* Calculating a and b */
b = (n*sumXY-sumX*sumY)/(n*sumX2-sumX*sumX);
a = (sumY - b*sumX)/n;
/* Displaying value of a and b */
printf("Values are: a=%0.2f and b = %0.2f",a,b);
printf("\nEquation of best fit is: y = %0.2f + %0.2fx",a,b);
getch();
return(0);
}
``````

## C Program Output: Linear Regression

```How many data points?
4
Enter data:
x = 0↲
y = -1↲
x = 2↲
y = 5↲
x = 5↲
y = 12↲
x = 7↲
y = 20↲
Values are: a=-1.14 and b=2.90
Equation of best fit is: y = -1.14 + 2.90x

Note: ↲ indicates ENTER is pressed.
```