simulation.nodes()

simulation.nodes([nodes])

If nodes is specified, sets the simulation’s nodes to the specified array of objects, initializing their positions and velocities if necessary, and then re-initializes any bound forces; returns the simulation. If nodes is not specified, returns the simulation’s array of nodes as specified to the constructor.

Each node must be an object. The following properties are assigned by the simulation:

• index - the node’s zero-based index into nodes
• x - the node’s current x-position
• y - the node’s current y-position
• vx - the node’s current x-velocity
• vy - the node’s current y-velocity

The position ⟨x,y⟩ and velocity ⟨vx,vy⟩ may be subsequently modified by forces and by the simulation. If either vx or vy is NaN, the velocity is initialized to ⟨0,0⟩. If either x or y is NaN, the position is initialized in a phyllotaxis arrangement, so chosen to ensure a deterministic, uniform distribution around the origin.

To fix a node in a given position, you may specify two additional properties:

• fx - the node’s fixed x-position
• fy - the node’s fixed y-position

At the end of each tick, after the application of any forces, a node with a defined node.fx has node.x reset to this value and node.vx set to zero; likewise, a node with a defined node.fy has node.y reset to this value and node.vy set to zero. To unfix a node that was previously fixed, set node.fx and node.fy to null, or delete these properties.

If the specified array of nodes is modified, such as when nodes are added to or removed from the simulation, this method must be called again with the new (or changed) array to notify the simulation and bound forces of the change; the simulation does not make a defensive copy of the specified array.