If r∈[0.75, 1], then the positive correlation is very strong; If r∈[- 1, -0.75], then the negative correlation is very strong;

If r∈(-0.75, -0.30) or r∈[0.30, 0.75], the correlation is average;

If r∈[-0.25, 0.25], the correlation is weak.

R has a formula to calculate, and you can look it up if necessary.