| 
 | virtual | 
Adds empty data point.
Call this method to add an empty data point. Use SetTreatNulls() to define series behavior when it encounters the empty data.
| dblX | Specifies X coordinate of empty data point. | 
| dwUserData | Specifies user defined data associated with data point. | 
| pDataPointFormat | A pointer to data point formatting options. |