Plates

# What is a plate?

A plate is a group of vertices that is repeated multiple times in the network. They typically represent a concept larger than a vertex like an agent in an ABM or some observations that are associated.

# How do you build them?

We’re redesigning how this is done but for now there are some handy helper functions to get you started.

Let’s say you have a class MyData that looks like this:

public static class MyData {
    public double x;
    public double y;

    public MyData(String x, String y) {
        this.x = Double.parseDouble(x);
        this.y = Double.parseDouble(y);
    }
}

This is an example of how you could pull in data from a csv file and run linear regression, using plates to build identical sections of the graph for each line of the csv.

/**
    * Each plate contains a linear regression model:
    * VertexY = VertexX * VertexM + VertexB
    * @param dataFileName The input data file defines, for each plate:
    *                          - the value of the input, VertexX
    *                          - the value of the observed output, VertexY
    */
public Plates buildPlates(String dataFileName) {
    //Parse the csv data to MyData objects
    List<MyData> allMyData = ReadCsv.fromFile(dataFileName)
            .asRowsDefinedBy(MyData.class)
            .load();

    DoubleVertex m = new GaussianVertex(0, 1);
    DoubleVertex b = new GaussianVertex(0, 1);
    VertexLabel xLabel = new VertexLabel("x");
    VertexLabel yLabel = new VertexLabel("y");

    //Build plates from each line in the csv
    Plates plates = new PlateBuilder<MyData>()
            .fromIterator(allMyData.iterator())
            .withFactory((plate, csvMyData) -> {

                ConstantDoubleVertex x = new ConstantDoubleVertex(csvMyData.x).setLabel(xLabel);
                DoubleVertex y = m.multiply(x).plus(b).setLabel(yLabel);

                DoubleVertex yObserved = new GaussianVertex(y, 1);
                yObserved.observe(csvMyData.y);

                // this labels the x and y vertex for later use
                plate.add(x);
                plate.add(y);
            })
            .build();

    //now you have access to the "x" from any one of the plates
    DoubleTensor valueForXAtCSVLine1 = plates.asList()
            .get(1) // get plate 1 which is built from csv line 1
            .<DoubleVertex>get(xLabel) //get the vertex that we labelled "x" in that plate
            .getValue(); //get the value from that vertex

    //Now run an inference algorithm on vertex m and vertex b and you have linear regression

    return plates;
}