/// <summary>
/// Example on how to use Stress Majorization with a small graph and Localized method.
/// </summary>
public static void RunStressMajorizationExample() {
//create a star graph where three nodes are connected to the center
GeometryGraph graph = new GeometryGraph();
graph.Nodes.Add(new Node());
graph.Nodes.Add(new Node());
graph.Nodes.Add(new Node());
graph.Nodes.Add(new Node());
//set initial positions, e.g., random
graph.Nodes[0].BoundaryCurve = CurveFactory.CreateRectangle(20, 10, new Point(5, 5));
graph.Nodes[1].BoundaryCurve = CurveFactory.CreateRectangle(20, 10, new Point(7, 10));
graph.Nodes[2].BoundaryCurve = CurveFactory.CreateRectangle(20, 10, new Point(7, 2));
graph.Nodes[3].BoundaryCurve = CurveFactory.CreateRectangle(20, 10, new Point(35, 1));
graph.Edges.Add(new Edge(graph.Nodes[0], graph.Nodes[1]));
graph.Edges.Add(new Edge(graph.Nodes[0], graph.Nodes[2]));
graph.Edges.Add(new Edge(graph.Nodes[0], graph.Nodes[3]));
//array with desired distances between the nodes for every edge
double[] idealEdgeLength=new double[graph.Edges.Count];
for (int i = 0; i < graph.Edges.Count; i++) {
idealEdgeLength[i] = 100; //all edges should have this euclidean length
}
//create stress majorization class and set the desired distances on the edges
StressMajorization majorizer = new StressMajorization();
majorizer.Positions = new List<Point>(graph.Nodes.Select(v=>v.Center));
majorizer.NodeVotings = new List<NodeVoting>(graph.Nodes.Count);
// initialize for every node an empty block
for (int i = 0; i < graph.Nodes.Count; i++) {
var nodeVote = new NodeVoting(i); //by default there is already a block with weighting 1
//optional: add second block with different type of edges, e.g., with stronger weight
//var secondBlock = new VoteBlock(new List<Vote>(), 100);
//nodeVote.VotingBlocks.Add(secondBlock);
//var block2=nodeVote.VotingBlocks[1]; //block could be accessed like this in a later stage
majorizer.NodeVotings.Add(nodeVote);
}
// for every edge set the desired distances by setting votings among the two end nodes.
Dictionary<Node,int> posDict=new Dictionary<Node, int>();
for (int i = 0; i < graph.Nodes.Count; i++) {
posDict[graph.Nodes[i]] = i;
}
var edges = graph.Edges.ToArray();
for (int i=0; i<graph.Edges.Count;i++) {
var edge = edges[i];
int nodeId1 = posDict[edge.Source];
int nodeId2 = posDict[edge.Target];
double idealDistance = idealEdgeLength[i];
double weight = 1 / (idealDistance * idealDistance);
var voteFromNode1 = new Vote(nodeId1, idealDistance, weight); // vote from node1 for node2
var voteFromNode2 = new Vote(nodeId2, idealDistance, weight); // vote from node2 for node1
// add vote of node1 to list of node2 (in first voting block)
majorizer.NodeVotings[nodeId2].VotingBlocks[0].Votings.Add(voteFromNode1);
// add vote of node2 to list of node1 (in first voting block)
majorizer.NodeVotings[nodeId1].VotingBlocks[0].Votings.Add(voteFromNode2);
}
//used localized method to reduce stress
majorizer.Settings=new StressMajorizationSettings();
majorizer.Settings.SolvingMethod=SolvingMethod.Localized;
List<Point> result = majorizer.IterateAll();
for (int i = 0; i < result.Count; i++) {
graph.Nodes[i].Center = result[i];
}
#if DEBUG && !SILVERLIGHT && !SHARPKIT
LayoutAlgorithmSettings.ShowGraph(graph);
#endif
}
static void AddStressFromProximityEdges(StressMajorization stressSolver,
List<Tuple<int, int, double, double>> proximityEdgesWithDistance) {
//set to check whether we already added forces between two nodes
var nodePairs = new HashSet<Tuple<int, int>>();
// set the corresponding forces/votings
foreach (var tuple in proximityEdgesWithDistance) {
int nodeId1 = tuple.Item1;
int nodeId2 = tuple.Item2;
if (nodeId1 > nodeId2) {
nodeId1 = tuple.Item2;
nodeId2 = tuple.Item1;
}
var tup = new Tuple<int, int>(nodeId1, nodeId2);
if (nodePairs.Contains(tup))
continue;
nodePairs.Add(tup);
double distance = tuple.Item3;
double weight = 1/(distance*distance);
var voteFromNode1 = new Vote(nodeId1, distance, weight); // vote from node1 for node2
var voteFromNode2 = new Vote(nodeId2, distance, weight); // vote from node2 for node1
if (tuple.Item4 <= 1) {
//nodes do not overlap
// add the votings, which represent forces, to the corresponding block.
stressSolver.NodeVotings[nodeId2].VotingBlocks[0].Votings.Add(voteFromNode1);
// add vote of node1 to list of node2
stressSolver.NodeVotings[nodeId1].VotingBlocks[0].Votings.Add(voteFromNode2);
}
else {
//edges where nodes do overlap
// add the votings, which represent forces, to the corresponding block.
stressSolver.NodeVotings[nodeId2].VotingBlocks[1].Votings.Add(voteFromNode1);
// add vote of node1 to list of node2
stressSolver.NodeVotings[nodeId1].VotingBlocks[1].Votings.Add(voteFromNode2);
// add vote of node2 to list of node1
}
}
}