The row or column indicates to which row or column this row/column data vector refers. Each row/column data vector deals only with one row or column at a time. If this row/column data vector is used ...

The vector form searches for a value in a single row or column and returns a corresponding value from another row or column, ...

The _init method does the setup of the row/column data vector. It also calls the super _init method. The _init method is called whenever you make an instance of the Row/Column Data Vector class, ...