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Published: Aug 16, 2019 License: BSD-3-Clause Imports: 8 Imported by: 0



Package layout defines functions for performing graph layout.



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type EadesR2

type EadesR2 struct {
	// Updates is the number of updates to perform.
	Updates int

	// Repulsion is the strength of the global
	// repulsive force between nodes in the
	// layout. It corresponds to C3 in the paper.
	Repulsion float64

	// Rate is the gradient descent rate. It
	// corresponds to C4 in the paper.
	Rate float64

	// Theta is the Barnes-Hut theta constant.
	Theta float64

	// Src is the source of randomness used
	// to initialize the nodes' locations. If
	// Src is nil, the global random number
	// generator is used.
	Src rand.Source
	// contains filtered or unexported fields

EadesR2 implements the graph layout algorithm essentially as described in "A heuristic for graph drawing", Congressus numerantium 42:149-160. The implementation here uses the Barnes-Hut approximation for global repulsion calculation, and edge weights are considered when calculating adjacent node attraction.

func (*EadesR2) Update

func (u *EadesR2) Update(g graph.Graph, layout LayoutR2) bool

Update is the EadesR2 spatial graph update function.

type GraphR2

type GraphR2 interface {
	LayoutNodeR2(id int64) NodeR2

GraphR2 is a graph with planar spatial representation of node positions.

type IsomapR2

type IsomapR2 struct{}

IsomapR2 implements a graph layout algorithm based on the Isomap non-linear dimensionality reduction method. Coordinates of nodes are computed by finding a Torgerson multidimensional scaling of the shortest path distances between all pairs of node in the graph. The all pair shortest path distances are calculated using the Floyd-Warshall algorithm and so IsomapR2 will not scale to large graphs. Graphs with more than one connected component cannot be laid out by IsomapR2.

func (IsomapR2) Update

func (IsomapR2) Update(g graph.Graph, layout LayoutR2) bool

Update is the IsomapR2 spatial graph update function.

type LayoutR2

type LayoutR2 interface {
	// IsInitialized returns whether the Layout is initialized.
	IsInitialized() bool

	// SetCoord2 sets the coordinates of the node with the given
	// id to coords.
	SetCoord2(id int64, coords r2.Vec)

	// Coord2 returns the coordinated of the node with the given
	// id in the graph layout.
	Coord2(id int64) r2.Vec

LayoutR2 implements graph layout updates and representations.

type NodeR2

type NodeR2 struct {
	Coord2 r2.Vec

NodeR2 is a graph node with planar spatial representation of its position. A NodeR2 is only valid when the graph.Node is not nil.

type OptimizerR2

type OptimizerR2 struct {

	// Updater is the function called for each call to Update.
	// It updates the OptimizerR2's spatial distribution of the
	// nodes in the backing graph.
	Updater func(graph.Graph, LayoutR2) bool
	// contains filtered or unexported fields

OptimizerR2 is a helper type that holds a graph and layout optimization state.

func NewOptimizerR2

func NewOptimizerR2(g graph.Graph, update func(graph.Graph, LayoutR2) bool) OptimizerR2

NewOptimizerR2 returns a new layout optimizer. If g implements LayoutR2 the layout will be updated into g, otherwise the OptimizerR2 will hold the graph layout. A nil value for update is a valid no-op layout update function.

func (OptimizerR2) Coord2

func (g OptimizerR2) Coord2(id int64) r2.Vec

Coord2 returns the location of the node with the given ID. The returned value is only valid if the node exists in the graph.

func (OptimizerR2) Edge

func (g OptimizerR2) Edge(uid, vid int64) graph.Edge

Edge returns the edge from u to v, with IDs uid and vid, if such an edge exists and nil otherwise. The node v must be directly reachable from u as defined by the From method.

func (OptimizerR2) From

func (g OptimizerR2) From(id int64) graph.Nodes

From returns all nodes that can be reached directly from the node with the given ID.

func (OptimizerR2) HasEdgeBetween

func (g OptimizerR2) HasEdgeBetween(xid, yid int64) bool

HasEdgeBetween returns whether an edge exists between nodes with IDs xid and yid without considering direction.

func (OptimizerR2) LayoutNodeR2

func (g OptimizerR2) LayoutNodeR2(id int64) NodeR2

LayoutNodeR2 implements the GraphR2 interface.

func (OptimizerR2) Node

func (g OptimizerR2) Node(id int64) graph.Node

Node returns the node with the given ID if it exists in the graph, and nil otherwise.

func (OptimizerR2) Nodes

func (g OptimizerR2) Nodes() graph.Nodes

Nodes returns all the nodes in the graph.

func (OptimizerR2) Update

func (g OptimizerR2) Update() bool

Update updates the locations of the nodes in the graph according to the provided update function. It returns whether the update function is able to further refine the graph's node locations.

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