Problems can also arise in a stacked chart if the X values of a successive series do not coincide with the first series. For instance, the first series of the chart could have x values at 2, 4, 6, and 8, while the second series has values at 3, 5, 7, and 9. A problem arises when the chart tries to discern where to place the first point of the second series. The point value that must be added to the Y value of the second series is somewhere between the first two points of the first series and is not explicitly part of the dataset.

Instead of not displaying the data set, C1Chart deals with this irregularity in a logical manner. It interpolates a virtual point in between the first and second point of the first series based on the slope of the line. This interpolated value is added to the second series’ Y value to find the new point for the stacked chart.