Is there a way to to get a scalar containing the sum of the off-diagonal
elements of a pre-defined matrix?
For instance, define matrix C as a correlation matrix. I want to know what
is the sum of correlations between the various elements in C. Therefore I
need the sum of all elements in C minus the sum of the diagonal elements
(-trace(C)-) and finally divide it by 2 (I am assuming matric C is
symetric).
