The GetCorrelation( obj1, obj2 ) command returns the correlation coefficient between the quantities-with-error obj1 and obj2.

The returned correlation is in the range .

If obj1 and obj2 are the same,  is returned.

If no correlation is defined between obj1 and obj2 (with SetCorrelation),  is returned.

If either or both of the quantities-with-error obj1 and obj2 have functional dependence on other quantities-with-error, Covariance is used to calculate their relative covariance, which is then converted to the correlation coefficient.

The relationship between the covariance  and correlation  is

where  and  are the errors in  and .