I am using PlantUML API to generate Activity Diagram.
I have used GraphViz before and used rank parameter to define layout
rank=LR [for left to right]
I am trying to find similiar thing in PlantUML where I can change its orientation to "Left to Right" instead of existing layout i.e. "Top to Bottom".
You can use the following command with State, Class, Component or Usecase diagrams:
left to right direction
A pretty good graphical example of how this works can be found in the Hitchhiker's Guide