Correlation

Correlation is a statistical measure that quantifies the degree of association or relationship between two variables. In other words, it helps us understand how two variables tend to move in relation to each other.

Correlation provides a straightforward way to examine the result. The correlation value falls within the range of [-1; 1]. Refer to the table below:

Correlation Value	Meaning
1	Perfect positive correlation: When one value increases, the other also increases, and vice versa.
0	No correlation: There is no visible relationship between the variables.
-1	Perfect negative correlation: When one value increases, the other decreases, and vice versa.

Correlation with Python:

To calculate correlation, we will use the function np.corrcoef() from NumPy with two parameters: the data sequences for which we want to find correlation. Take a look at the example:


              123456789
            
import pandas as pd
import numpy as np

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

# Calculating correlation 
corr = np.corrcoef(df['Store_Area'], df['Items_Available'])[0,1]

print(corr)

Here, we extracted the value at index [0, 1], just like in the case of covariance. In the previous chapter, we obtained the value 74955.85, and interpreting the result of the covariation function can be challenging. However, in this case, we can conclude that the values are strongly related.

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Seção 4. Capítulo 2