How to set edge's length proportional to edge's value

Question

Using JDK 1.7+Jung2.

I have a similarity matrix and want to analyze it graphically using jung2 graphs. My dataset is composed by data like:

object1 object2 0.54454
object1 object3 0.45634
object2 object3 0.90023
[..]

For each line, the value represents the similarity between the previous objects (i.e.: object1 has 0.54454 similarity with object2)

I want to create a graph where the distance between vertices is proportional to their edge value. For the example above, the object1 would be placed closer to object2 than to object3, because sim(object1,object2) > sim(object2,object3).

How can I achieve such task using Jung2? Default layouts dont seem to do this.

Answer 1

This depends on the layout that you intend to use. For the SpringLayout, you can pass a Transformer to the constructor as the length_function parameter, that you can simply implement as

class EdgeLengthTransformer implements Transformer<Edge, Integer> {
    @Override
    public Integer transform(Edge edge) {
        int minLength = 100; // Length for similarity 1.0
        int maxLength = 500; // Length for similarity 0.0
        Vertex v0 = graph.getSource(edge);
        Vertex v1 = graph.getDest(edge);
        float similarity = obtainSimilarityFromYourDataset(v0, v1);
        int length = (int)(minLength + (1.0 - similarity) * (maxLength - minLength));
        return length;
    }
}

You'll always have to take into account that - depending on the structure of the graph - it might simply not be possible to lay out the vertices as desired. For example, if the similarities do not obey the http://en.wikipedia.org/wiki/Triangle_inequality , then there is no suitable embedding of these similarities into the 2D space.