Detailed explanation of similarity based on Pearson correlation coefficient in Java

Recently, I was reading collective wisdom programming. Compared with other machine learning books, this book has many cases, which is closer to reality, and it is also very suitable for our Xiaobai who is ready to learn machine learning.

The algorithm of Pearson similarity calculation is still very simple and easy to implement. Only the variables X, y, the product XY, the square of X, and the sum of the squares of Y are required. The data test set used in my code comes from the book collective wisdom programming. The code is as follows: