/* An actor that outputs a random sequence with a Rician distribution.

 Copyright (c) 1998-2014 The Regents of the University of California.
 All rights reserved.
 Permission is hereby granted, without written agreement and without
 license or royalty fees, to use, copy, modify, and distribute this
 software and its documentation for any purpose, provided that the above
 copyright notice and the following two paragraphs appear in all copies
 of this software.

 IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY
 FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
 ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF
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 INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE
 PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND THE UNIVERSITY OF
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 COPYRIGHTENDKEY

 */
package ptolemy.actor.lib;

import ptolemy.data.DoubleToken;
import ptolemy.data.expr.Parameter;
import ptolemy.data.type.BaseType;
import ptolemy.kernel.CompositeEntity;
import ptolemy.kernel.util.IllegalActionException;
import ptolemy.kernel.util.NameDuplicationException;

///////////////////////////////////////////////////////////////////
//// Rician

/**
 <p>Produce a random sequence with a Rician distribution.
 A Rician random variable is defined as follows:
 Let Z = sqrt(X<sup>2</sup> + Y<sup>2</sup>), where X and Y are statistically
 independent Gaussian random variables with means given by parameters
 <i>xMean</i> and <i>yMean</i> respectively, and common variance given by
 parameter <i>standardDeviation</i>.
 </p><p>
 The default values of <i>xMean</i> and <i>yMean</i> are both set to be zero,
 in which the distribution is also called a Rayleigh distribution. Hence,
 the actor is by default a Rayleigh random generator.
 </p><p>
 On each iteration, a new random number is produced. The output port
 is of type DoubleToken. The values that are generated are independent
 and identically distributed with the means and the standard deviation
 given by parameters. In addition, the seed can be specified as a
 parameter to control the sequence that is generated.</p>

 @author Ye Zhou
 @version $Id$
 @since Ptolemy II 3.0
 @Pt.ProposedRating Green (eal)
 @Pt.AcceptedRating Green (bilung)
 @see ptolemy.actor.lib.Bernoulli
 @see ptolemy.actor.lib.DiscreteRandomSource
 @see ptolemy.actor.lib.Triangular
 @see ptolemy.actor.lib.Uniform
 */
public class Rician extends RandomSource {
    /** Construct an actor with the given container and name.
     *  @param container The container.
     *  @param name The name of this actor.
     *  @exception IllegalActionException If the actor cannot be contained
     *   by the proposed container.
     *  @exception NameDuplicationException If the container already has an
     *   actor with this name.
     */
    public Rician(CompositeEntity container, String name)
            throws NameDuplicationException, IllegalActionException {
        super(container, name);

        output.setTypeEquals(BaseType.DOUBLE);

        xMean = new Parameter(this, "xMean", new DoubleToken(0.0));
        xMean.setTypeEquals(BaseType.DOUBLE);

        yMean = new Parameter(this, "yMean", new DoubleToken(0.0));
        yMean.setTypeEquals(BaseType.DOUBLE);

        standardDeviation = new Parameter(this, "standardDeviation",
                new DoubleToken(1.0));
        standardDeviation.setTypeEquals(BaseType.DOUBLE);
    }

    ///////////////////////////////////////////////////////////////////
    ////                     ports and parameters                  ////

    /** The mean of the random number along the X-axis.
     *  This parameter contains a DoubleToken, initially with value 0.0.
     */
    public Parameter xMean;

    /** The mean of the random number along the Y-axis.
     *  This parameter contains a DoubleToken, initially with value 0.0.
     */
    public Parameter yMean;

    /** The standard deviation of the random number.
     *  This parameter contains a DoubleToken, initially with value 1.0.
     */
    public Parameter standardDeviation;

    ///////////////////////////////////////////////////////////////////
    ////                         public methods                    ////

    /** Send a random number with a Rician distribution to the output.
     *  This number is only changed in the prefire() method, so it will
     *  remain constant throughout an iteration.
     *  @exception IllegalActionException If there is no director.
     */
    @Override
    public void fire() throws IllegalActionException {
        super.fire();
        output.send(0, new DoubleToken(_current));
    }

    ///////////////////////////////////////////////////////////////////
    ////                         protected methods                 ////

    /** Generate a new random number.
     *  @exception IllegalActionException If parameter values are incorrect.
     */
    @Override
    protected void _generateRandomNumber() throws IllegalActionException {
        double xMeanValue = ((DoubleToken) xMean.getToken()).doubleValue();
        double yMeanValue = ((DoubleToken) yMean.getToken()).doubleValue();
        double standardDeviationValue = ((DoubleToken) standardDeviation
                .getToken()).doubleValue();
        double xRawNum = _random.nextGaussian();
        double yRawNum = _random.nextGaussian();
        _current = java.lang.Math.sqrt(java.lang.Math
                .pow(xRawNum * standardDeviationValue + xMeanValue, 2)
                + java.lang.Math
                        .pow(yRawNum * standardDeviationValue + yMeanValue, 2));
    }

    ///////////////////////////////////////////////////////////////////
    ////                         private variables                 ////
    // The random number for the current iteration.
    private double _current;
}