Determines whether or not gaps (i.e. {nan} or missing values) in the provided data arrays are connected.

Sets the area to fill with a solid color. Defaults to *none* unless this trace is stacked, then it gets *tonexty* (*tonextx*) if `orientation` is *v* (*h*) Use with `fillcolor` if not *none*. *tozerox* and *tozeroy* fill to x=0 and y=0 respectively. *tonextx* and *tonexty* fill between the endpoints of this trace and the endpoints of the trace before it, connecting those endpoints with straight lines (to make a stacked area graph); if there is no trace before it, they behave like *tozerox* and *tozeroy*. *toself* connects the endpoints of the trace (or each segment of the trace if it has gaps) into a closed shape. *tonext* fills the space between two traces if one completely encloses the other (eg consecutive contour lines), and behaves like *toself* if there is no trace before it. *tonext* should not be used if one trace does not enclose the other. Traces in a `stackgroup` will only fill to (or be filled to) other traces in the same group. With multiple `stackgroup`s 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.

Only relevant when `stackgroup` is used, and only the first `groupnorm` found in the `stackgroup` will be used - including if `visible` is *legendonly* but not if it is `false`. Sets the normalization for the sum of this `stackgroup`. With *fraction*, the value of each trace at each location is divided by the sum of all trace values at that location. *percent* is the same but multiplied by 100 to show percentages. If there are multiple subplots, or multiple `stackgroup`s on one subplot, each will be normalized within its own set.

Do the hover effects highlight individual points (markers or line points) or do they highlight filled regions? If the fill is *toself* or *tonext* and there are no markers or text, then the default is *fills*, otherwise it is *points*.