This function examines two sets of data to determine the degree of relationship
between the two sets.
The result will be a decimal between 0 and 1.
The larger the result, the greater the correlation.
In Table 1 the Monthly temperature is compared against the Sales of air conditioning units.
The correlation shows that there is an 0.864 relationship between the data.
In Table 2 the Cost of advertising has been compared to Sales.
It can be formatted as percentage % to show a more meaningful result.