Stacked spline areas are multi-series charts with two or more spline areas. Each spline area is filled beween the smooth curve line and the cumulative area of the previous series (or the horizontal baseline, for the first series) with a different color. Multi-series stacked areas appear one above the others. One series may never cover other series, because they always fill separate areas.
Our Global Sales demo charts show three separate continuous smooth curve lines joining the points at the intersection of each year value between 2000 and 2017 and the cumulative number of products sold in US, France or UK in that year. Each new area is added on top of the previous cumulative area. The zone between the last area and previous cumulative area - or the horizontal baseline for the first series - is painted with a different palette color. These are multi-series charts and each series line and area get their own color. Unlike grouped areas, stacked areas always cover separate zones that do not intersect each other.