luc062.c

Metadata

• Author — Amit Dutta
• Last updated — 08 Feb 2026
• License — MIT License (See the LICENSE file for details)

Problem Statement

Problem Statement

For the following set of n data points (x, y), write a program to compute the correlation coefficient r.

Source Code

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#include <stdio.h>
#include <math.h>
#include <stdlib.h>

int main()
{
    double x[] = {34.22, 39.87, 41.85, 43.23, 40.06, 53.29, 53.29, 54.14, 49.12, 40.71, 55.15};
    double y[] = {102.43, 100.93, 97.43, 97.81, 98.32, 98.32, 100.07, 97.08, 91.59, 94.85, 94.65};
    
    int n = 11, i;
    double sum_x = 0, sum_y = 0, sum_xy = 0, sum_x2 = 0, sum_y2 = 0;
    double numerator, denominator, r;

    for (i = 0; i < n; i++)
    {
        sum_x += x[i];
        sum_y += y[i];
        sum_xy += x[i] * y[i];
        sum_x2 += x[i] * x[i];
        sum_y2 += y[i] * y[i];
    }

    numerator = (n * sum_xy) - (sum_x * sum_y);
    denominator = sqrt((n * sum_x2 - sum_x * sum_x) * (n * sum_y2 - sum_y * sum_y));

    if (denominator != 0)
        r = numerator / denominator;
    else
        r = 0; // Avoid division by zero

    printf("Correlation coefficient (r) = %.4f\n", r);

    return 0;
}