I have learned Correlation Coefficient in statistics class when I was a student, but have no impression on Coefficient of Determination or R-Squared. So the first problem for this R-Squared is “What can I do with it?”

I find the answer here:

How well does your regression equation truly represent your set of data? One of the ways to determine the answer to this question is to exam the correlation coefficient and the coefficient of determination.

Here is two examples how to compute Coefficient of Determination:

http://online.stat.psu.edu/online/development/stat501/04linear_assoc/02linear_assoc_r2.html

Following is the related Youtube Video I think maybe useful for you:

R-Squared or Coefficient of Determination by Khan Academy:

Coefficient of determination (r-squared):

Maths Tutorial: Coefficient of Determination – r squared (statistics)

Coefficient Of Determination (r squared)

Posted by 52nlp