getTrendLines
getTrendLines() method
Collection of series trend lines. Read-only ITrendlineCollection.
TrendLines are available (not null) for data series in unstacked 2-D area, bar, column, line, stock, xy (scatter), and bubble charts. A trendline are not available for data series in any chart type that is stacked or 3-D. Trendlines are also not available for radar, pie, surface, or doughnut charts.