Sxy Command

Sxy( <List of Points> ): Calculates the statistic $\sum xy - \frac{(\sum x) (\sum y)}{n}$ using the coordinates of the given points.
Sxy( <List of Numbers>, <List of Numbers> ): Calculates the statistic $\sum xy - \frac{(\sum x) (\sum y)}{n}$ , where x are the values in the first list, and y are the values in the second given list.