Return the current alpha of the simulation, which defaults to 1.
alpha is roughly analogous to temperature in simulated annealing. It decreases over time as the simulation “cools down”. When alpha reaches alphaMin, the simulation stops; see simulation.restart.
Set the current alpha to the specified number in the range [0,1] and return this simulation. The default is 1.
alpha is roughly analogous to temperature in simulated annealing. It decreases over time as the simulation “cools down”. When alpha reaches alphaMin, the simulation stops; see simulation.restart.
Current alpha of simulation.
Return the current alpha decay rate, which defaults to 0.0228… = 1 - pow(0.001, 1 / 300) where 0.001 is the default minimum alpha.
Set the alpha decay rate to the specified number in the range [0,1] and return this simulation. The default is 0.0228… = 1 - pow(0.001, 1 / 300) where 0.001 is the default minimum alpha.
The alpha decay rate determines how quickly the current alpha interpolates towards the desired target alpha; since the default target alpha is zero, by default this controls how quickly the simulation cools. Higher decay rates cause the simulation to stabilize more quickly, but risk getting stuck in a local minimum; lower values cause the simulation to take longer to run, but typically converge on a better layout. To have the simulation run forever at the current alpha, set the decay rate to zero; alternatively, set a target alpha greater than the minimum alpha.
Alpha decay rate.
Return the current minimum alpha value, which defaults to 0.001.
Set the minimum alpha to the specified number in the range [0,1] and return this simulation. The default is 0.001. The simulation’s internal timer stops when the current alpha is less than the minimum alpha. The default alpha decay rate of ~0.0228 corresponds to 300 iterations.
Minimum alpha of simulation.
Returns the current target alpha value, which defaults to 0.
Set the current target alpha to the specified number in the range [0,1] and return this simulation. The default is 0.
Alpha target value.
Return the node closest to the position [x,y] with the given search radius. If radius is not specified, it defaults to infinity. If there is no node within the search area, returns undefined.
x-coordinate
y-coordinate
Optional radius: numberOptional search radius. Defaults to infinity.
Return the force with the specified name, or undefined if there is no such force. (By default, new simulations have no forces.)
Given that it is in general not known, what type of force has been registered under a specified name, use the generic to cast the result to the appropriate type, if known.
Name of the registered force.
If force is specified, assigns the force for the specified name and returns this simulation. To remove the force with the given name, pass null as the force.
Returns the simulation’s array of nodes as specified to the constructor.
Set the simulation’s nodes to the specified array of objects, initialize their positions and velocities if necessary, and then re-initialize any bound forces; Returns the simulation.
Each node must be an object. The following properties are assigned by the simulation:
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.
To fix a node in a given position, you may specify two additional properties:
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.
Return the first currently-assigned listener matching the specified typenames, if any.
The typenames is a string containing one or more typename separated by whitespace. Each typename is a type, optionally followed by a period (.) and a name, such as "tick.foo" and "tick.bar"; the name allows multiple listeners to be registered for the same type. The type must be one of the following: "tick" (after each tick of the simulation’s internal timer) or "end" (after the simulation’s timer stops when alpha < alphaMin).
Sets the event listener for the specified typenames and returns this simulation. If an event listener was already registered for the same type and name, the existing listener is removed before the new listener is added. If listener is null, removes the current event listeners for the specified typenames, if any. When a specified event is dispatched, each listener will be invoked with the this context as the simulation.
Returns this simulation’s current random source which defaults to a fixed-seed linear congruential generator. See also random.source.
Returns this simulation’s current random source which defaults to a fixed-seed linear congruential generator. See also random.source.
Sets the function used to generate random numbers; this should be a function that returns a number between 0 (inclusive) and 1 (exclusive).
The function used to generate random numbers.
Restart the simulation’s internal timer and return the simulation. In conjunction with simulation.alphaTarget or simulation.alpha, this method can be used to “reheat” the simulation during interaction, such as when dragging a node, or to resume the simulation after temporarily pausing it with simulation.stop.
Stop the simulation’s internal timer, if it is running, and return the simulation. If the timer is already stopped, this method does nothing. This method is useful for running the simulation manually; see simulation.tick.
Manually steps the simulation by the specified number of iterations, and returns the simulation. If iterations is not specified, it defaults to 1 (single step).
For each iteration, it increments the current alpha by (alphaTarget - alpha) × alphaDecay; then invokes each registered force, passing the new alpha; then decrements each node’s velocity by velocity × velocityDecay; lastly increments each node’s position by velocity.
This method does not dispatch events; events are only dispatched by the internal timer when the simulation is started automatically upon creation or by calling simulation.restart. The natural number of ticks when the simulation is started is ⌈log(alphaMin) / log(1 - alphaDecay)⌉; by default, this is 300.
Optional iterations: numberReturn the current target alpha value, which defaults to 0.4.
Set the velocity decay factor to the specified number in the range [0,1] and return this simulation. The default is 0.4.
The decay factor is akin to atmospheric friction; after the application of any forces during a tick, each node’s velocity is multiplied by 1 - decay. As with lowering the alpha decay rate, less velocity decay may converge on a better solution, but risks numerical instabilities and oscillation.
Velocity Decay.
A Force Simulation
The first generic refers to the type of the datum associated with a node in the simulation. The second generic refers to the type of the datum associated with a link in the simulation, if applicable.