Creating data in Prefuse

I am new to Prefuse. The demo examples are all loaded data from a file/database. Is there any way to create the data dynamically instead of loading from file. For example, I want to create a tree data structure and visualize this. Any simple working example would be really helpful for me.

I've just been attacking this problem. Here's a tweaked version of Example.java which shows one way to make it happen.

Instead of loading data from socialnet.xml, I'm generating it programatically (based on Aggregate.java but without the aggregation stuff) and adding one field to each Node and each Edge. The Node field is a simple boolean flag which controls the colour it's rendered; the Edge field is a label - but it's not being rendered yet. I'm still working on that one! :-)

The question-specific code is in makeGraph(). The basic approach is to create a Table (well, one each for nodes and edges), and add columns to those tables defining the shape of the data; then when you add your nodes and edges, you can add the corresponding data. One gotcha is that for edges you must include columns for the edge's source/target nodes - see the Graph and Table documentation for more details. There are other ways to do this (e.g. involving Schema) but I haven't sussed them out yet.

Hope this helps.

import javax.swing.JFrame;

import prefuse.Constants;
import prefuse.Display;
import prefuse.Visualization;
import prefuse.action.ActionList;
import prefuse.action.RepaintAction;
import prefuse.action.assignment.ColorAction;
import prefuse.action.assignment.DataColorAction;
import prefuse.action.layout.graph.ForceDirectedLayout;
import prefuse.activity.Activity;
import prefuse.controls.DragControl;
import prefuse.controls.PanControl;
import prefuse.controls.ZoomControl;
import prefuse.data.Edge;
import prefuse.data.Graph;
import prefuse.data.Node;
import prefuse.data.Table;
import prefuse.render.DefaultRendererFactory;
import prefuse.render.EdgeRenderer;
import prefuse.render.Renderer;
import prefuse.render.ShapeRenderer;
import prefuse.util.ColorLib;
import prefuse.visual.VisualItem;

public class Example extends Display {

    private Graph makeGraph() {

        // Create tables for node and edge data, and configure their columns.
        Table nodeData = new Table();
        Table edgeData = new Table(0,1);
        nodeData.addColumn("flag", boolean.class);
        edgeData.addColumn(Graph.DEFAULT_SOURCE_KEY, int.class);
        edgeData.addColumn(Graph.DEFAULT_TARGET_KEY, int.class);
        edgeData.addColumn("label", String.class);
        // Need more data in your nodes or edges?  Just add more
        // columns.

        // Create Graph backed by those tables.  Note that I'm
        // creating a directed graph here also.
        Graph g = new Graph(nodeData, edgeData, true);

        // Create some nodes and edges, each carrying some data.
        // There are surely prettier ways to do this, but for the
        // example it gets the job done.
        for ( int i=0; i<3; ++i ) {
            Node n1 = g.addNode();
            Node n2 = g.addNode();
            Node n3 = g.addNode();
            n1.setBoolean("flag", false);
            n2.setBoolean("flag", true);
            n3.setBoolean("flag", true);
            Edge e1 = g.addEdge(n1, n2);
            Edge e2 = g.addEdge(n1, n3);
            Edge e3 = g.addEdge(n2, n3);
            e1.setString("label", "a");
            e2.setString("label", "a");
            e3.setString("label", "a");
        }
        Edge e4 = g.getEdge(g.addEdge(0, 3));
        Edge e5 = g.getEdge(g.addEdge(3, 6));
        Edge e6 = g.getEdge(g.addEdge(6, 0));
        e4.setString("label", "b");
        e5.setString("label", "b");
        e6.setString("label", "b");
        return g;
    }

    public Example() {

        super(new Visualization());

        Graph graph = makeGraph();

        m_vis.addGraph("graph", graph);
        m_vis.setInteractive("graph.edges", null, false);
        m_vis.setValue("graph.nodes", null, VisualItem.SHAPE,
                new Integer(Constants.SHAPE_ELLIPSE));

        Renderer nodeR = new ShapeRenderer(20);
        EdgeRenderer edgeR = new EdgeRenderer(prefuse.Constants.EDGE_TYPE_CURVE, prefuse.Constants.EDGE_ARROW_FORWARD);

        DefaultRendererFactory drf = new DefaultRendererFactory();
        drf.setDefaultRenderer(nodeR);
        drf.setDefaultEdgeRenderer(edgeR);
        m_vis.setRendererFactory(drf);

        int[] palette = new int[] {
            ColorLib.rgb(255,180,180), ColorLib.rgb(190,190,255)
        };
        ColorAction nStroke = new ColorAction("graph.nodes", VisualItem.STROKECOLOR);
        nStroke.setDefaultColor(ColorLib.gray(100));

        DataColorAction nFill = new DataColorAction("graph.nodes", "flag",
            Constants.NOMINAL, VisualItem.FILLCOLOR, palette);
        ColorAction edges = new ColorAction("graph.edges",
            VisualItem.STROKECOLOR, ColorLib.gray(200));
        ColorAction arrow = new ColorAction("graph.edges",
            VisualItem.FILLCOLOR, ColorLib.gray(200));
        ActionList color = new ActionList();
        color.add(nStroke);
        color.add(nFill);
        color.add(edges);
        color.add(arrow);

        ActionList layout = new ActionList(Activity.INFINITY);
        layout.add(new ForceDirectedLayout("graph"));
        layout.add(new RepaintAction());

        m_vis.putAction("color", color);
        m_vis.putAction("layout", layout);

        setSize(720, 500); // set display size
        pan(360, 250);
        setHighQuality(true);
        addControlListener(new DragControl());
        addControlListener(new PanControl());
        addControlListener(new ZoomControl());

        m_vis.run("color");
        m_vis.run("layout");

    }

    public static void main(String[] argv) {
        Example ex = new Example();
        JFrame frame = new JFrame("prefuse example");
        frame.getContentPane().add(ex);
        frame.pack();           // layout components in window
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true); // show the window
    }

}