///////////////////////////////////////////////////////////////////////////////
// For information as to what this class does, see the Javadoc, below.       //
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// Scheines, Joseph Ramsey, and Clark Glymour.                               //
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package edu.cmu.tetrad.study.gene.tetrad.gene.history;

import edu.cmu.tetrad.util.dist.Distribution;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.util.ArrayList;
import java.util.List;

/**
 * <p>Implements a linear update function, Gi.0 = L(Parents(G0.0)) + ei, where P
 * is a polynomial function and ei is a random noise term.
 *
 * @author josephramsey
 */
public class LinearFunction implements UpdateFunction {
    static final long serialVersionUID = 23L;

    /**
     * The wrapped polynomial function that's doing all the work.
     *
     * @serial
     */
    private final PolynomialFunction polynomialFunction;

    //=========================CONSTRUCTORS=============================//

    /**
     * Constructs a polyomial function where each factor is given a zero
     * polynomial.
     */
    public LinearFunction(LagGraph lagGraph) {
        if (lagGraph == null) {
            throw new NullPointerException("Lag graph must not be null.");
        }

        this.polynomialFunction = new PolynomialFunction(lagGraph);
        IndexedLagGraph connectivity = this.polynomialFunction.getIndexedLagGraph();

        for (int i = 0; i < connectivity.getNumFactors(); i++) {
            List terms = new ArrayList();

            // Intercept.
            terms.add(new PolynomialTerm(0.0, new int[0]));

            int numParents = connectivity.getNumParents(i);
            for (int j = 0; j < numParents; j++) {

                int[] vars = {j};
                terms.add(new PolynomialTerm(1.0 / (double) numParents, vars));
            }
            Polynomial p = new Polynomial(terms);
            this.polynomialFunction.setPolynomial(i, p);
        }
    }

    /**
     * Generates a simple exemplar of this class to test serialization.
     */
    public static LinearFunction serializableInstance() {
        return new LinearFunction(BasicLagGraph.serializableInstance());
    }

    //============================PUBLIC METHODS==========================//

    /**
     * Returns the value of the function.
     */
    public double getValue(int factorIndex, double[][] history) {
        return this.polynomialFunction.getValue(factorIndex, history);
    }

    /**
     * Returns the indexed connectivity.
     */
    public IndexedLagGraph getIndexedLagGraph() {
        return this.polynomialFunction.getIndexedLagGraph();
    }

    /**
     * Sets the intercept for the given factor.
     */
    public boolean setIntercept(String factor, double intercept) {
        IndexedLagGraph connectivity =
                this.polynomialFunction.getIndexedLagGraph();

        int factorIndex = connectivity.getIndex(factor);

        return setIntercept(factorIndex, intercept);
    }

    /**
     * Sets the intercept for the given factor.
     */
    public boolean setIntercept(int factor, double intercept) {
        Polynomial p = this.polynomialFunction.getPolynomial(factor);
        PolynomialTerm term = p.findTerm(new int[0]);
        if (term == null) {
            return false;
        }

        term.setCoefficient(intercept);
        return true;
    }

    /**
     * Sets the intercept for the given factor.
     */
    public boolean setCoefficient(String factor, LaggedFactor parent,
                                  double intercept) {
        IndexedLagGraph connectivity = this.polynomialFunction.getIndexedLagGraph();

        int factorIndex = connectivity.getIndex(factor);
        int parentIndex = connectivity.getIndex(factor, parent);

        return setCoefficient(factorIndex, parentIndex, intercept);
    }

    /**
     * Sets the coefficient for the given parent of the given factor.
     */
    public boolean setCoefficient(int factor, int parent, double coefficient) {

        Polynomial p = this.polynomialFunction.getPolynomial(factor);
        PolynomialTerm term = p.findTerm(new int[]{parent});

        if (term == null) {
            return false;
        }

        term.setCoefficient(coefficient);
        return true;
    }

    /**
     * Method setIntenalNoiseModel
     *
     * @param factor
     * @param distribution
     */
    public void setErrorDistribution(int factor, Distribution distribution) {
        this.polynomialFunction.setErrorDistribution(factor, distribution);
    }

    /**
     * Returns the error distribution for the <code>factor</code>'th factor.
     *
     * @param factor the factor in question.
     * @return the error distribution for <code>factor</code>.
     */
    public Distribution getErrorDistribution(int factor) {
        return this.polynomialFunction.getErrorDistribution(factor);
    }

    /**
     * Prints out the linear function of each factor of its parents.
     */
    public String toString() {
        StringBuilder buf = new StringBuilder();
        IndexedLagGraph connectivity = this.polynomialFunction.getIndexedLagGraph();
        buf.append("\n\nLinear Function:");
        for (int i = 0; i < connectivity.getNumFactors(); i++) {
            buf.append("\n\tFactor ").append(connectivity.getFactor(i)).append(" --> ").append(this.polynomialFunction.getPolynomial(i));
        }
        return buf.toString();
    }

    /**
     * Returns the number of factors in the history. This is used to set up the
     * initial history array.
     */
    public int getNumFactors() {
        return this.polynomialFunction.getNumFactors();
    }

    /**
     * Returns the max lag of the history. This is used to set up the initial
     * history array.
     */
    public int getMaxLag() {
        return this.polynomialFunction.getMaxLag();
    }

    /**
     * Adds semantic checks to the default deserialization method. This method
     * must have the standard signature for a readObject method, and the body of
     * the method must begin with "s.defaultReadObject();". Other than that, any
     * semantic checks can be specified and do not need to stay the same from
     * version to version. A readObject method of this form may be added to any
     * class, even if Tetrad sessions were previously saved out using a version
     * of the class that didn't include it. (That's what the
     * "s.defaultReadObject();" is for. See J. Bloch, Effective Java, for help.
     */
    private void readObject(ObjectInputStream s)
            throws IOException, ClassNotFoundException {
        s.defaultReadObject();

        if (this.polynomialFunction == null) {
            throw new NullPointerException();
        }
    }
}





