stackgroup

Set several scatter traces (on the same subplot) to the same stackgroup in order to add their y values (or their x values if orientation is "h"). If blank or omitted this trace will not be stacked. Stacking also turns fill on by default, using "tonexty" ("tonextx") if orientation is "h" ("v") and sets the default mode to "lines" irrespective of point count. You can only stack on a numeric (linear or log) axis. Traces in a stackgroup will only fill to (or be filled to) other traces in the same group. With multiple stackgroups or some traces stacked and some not, if fill-linked traces are not already consecutive, the later ones will be pushed down in the drawing order. Default: "".