X and Y are vectors of the same length.
Get of positions that are not NULL in both X and Y, and calculate the sum of squares of the elements in X on these positions.
Please note that the data type of the result is always DOUBLE, even if the data type of X and Y is INT or LONG.
$ contextSum2(1 2 3, 10 NULL 30); 10 $ contextSum2(1 2 3, true false true); 14
Related functions: contextCount, contextSum