Any guru can give some information about the force direct graphic, I'm confused why the nodes drawed with force direct graphic are not affected by gravity and fall down?

[duxianpeng]

[Jochem Schulenklopper]

Gravity is a valid force, but typically not specified in a force-directed graph. The forces in a force-directed graph are modelled as spring forces (so, along the connections between the nodes). Would gravity be a force modelled in a force-directed graph, some spring (connected to the bottom?) would have to be attached to the nodes.

So, no need to fix/change.

[Daniel Shiffman]

Thanks for the comment and feedback all.