Summary  
This chapter shows how to implement functions to compute covariance and correlation between numerical datasets by processing arrays and applying statistical formulas.  

General domain of usage  
Data analysis

import unittest
import pandas as pd
import numpy as np

def _dynamic_test(test_case, condition, success_msg, failure_msg):
    if condition:
        test_case._testMethodName = success_msg
        test_case.assertTrue(True, success_msg)
    else:
        test_case._testMethodName = failure_msg
        test_case.fail(failure_msg)


class TestCovariance(unittest.TestCase):
    def test_covariance(self):
        import user_code

        df = pd.read_csv(
            'https://codefinity-content-media.s3.eu-west-1.amazonaws.com/a849660e-ddfa-4033-80a6-94a1b7772e23/update/Stores.csv'
        )

        expected_cov = np.cov(df['Daily_Customer_Count'], df['Items_Available'])[0, 1]

        condition = abs(user_code.cov - expected_cov) < 1e-6

        _dynamic_test(
            self,
            condition,
            "The covariance is calculated correctly.",
            "The covariance is incorrect. Check your calculation."
        )


class TestCorrelation(unittest.TestCase):
    def test_correlation(self):
        import user_code

        df = pd.read_csv(
            'https://codefinity-content-media.s3.eu-west-1.amazonaws.com/a849660e-ddfa-4033-80a6-94a1b7772e23/update/Stores.csv'
        )

        expected_corr = np.corrcoef(df['Daily_Customer_Count'], df['Items_Available'])[0, 1]

        condition = abs(user_code.corr - expected_corr) < 1e-6

        _dynamic_test(
            self,
            condition,
            "The correlation is calculated correctly.",
            "The correlation is incorrect. Check your calculation."
        )


if __name__ == "__main__":
    unittest.main()


test_code.py

Learn core statistical concepts used in data analysis with Python. The course covers descriptive statistics, including mean, median, mode, variance, and standard deviation, as well as sampling, probability distributions, the Central Limit Theorem, and outlier detection.

Calculate Covariance and Correlation

Soluzione