The data item is taken from the ith data point and the jth data column. If no data have been taken, the returned value is NIL.
|The returned value.|
No datum acquired yet.
|Point number, zero-based. If PointNum is out of range, a value from the last or acquired point is returned.|
|NIL||Always return a value from the last acquired point.|
Data column, with a range of 0 to 2. The meaning of the data in each column is given in the Ocv.DataCol() description.