Specifies the orientation of the gradient when the gradient type is linear.
string
vertical
vertical,
horizontal
Area,
AreaLine,
Bar,
BarLine,
Boxplot,
Circular,
Correlation,
DotLine,
Dotplot,
Fish,
Gantt,
Genome,
Heatmap,
Line,
Map,
Network,
ParallelCoordinates,
Pie,
Sankey,
Scatter2D,
Scatter3D,
ScatterBubble2D,
Stacked,
StackedLine,
StackedPercent,
StackedPercentLine,
TagCloud,
Tree,
Treemap,
Venn