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 * 
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 * 
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package jhplot.math.num.random;


/**
 * 

 * A random variable generator for the Bernoulli distribution.
 * 
 * 

 * References:
 * 

 * 
Wikipedia contributors, "Bernoulli Distribution," Wikipedia, The Free
 * Encyclopedia, 
 * http://en.wikipedia.org/wiki/Bernoulli_distribution
 * 
 * 

 * 
 * @since 1.3
 * @version $Revision: 1.3 $ $Date: 2007/11/18 23:51:19 $
 */
public class BernoulliRandomVariable extends AbstractDiscreteRandomVariable {

    /** the probability of success. */
    private double probabilityOfSuccess;

    /**
     * Default constructor. The probability of success is set to 0.5.
     */
    public BernoulliRandomVariable() {
        this(0.5);
    }

    /**
     * Create a random variable with the given probability of success.
     * 
     * @param p the probability of success.
     */
    public BernoulliRandomVariable(double p) {
        this(p, new RandomRNG());
    }

    /**
     * Create a random variable with the given probability of success and source
     * generator.
     * 
     * @param p the probability of success.
     * @param source the source generator.
     */
    public BernoulliRandomVariable(double p, RNG source) {
        super(source);
        setProbabilityOfSuccess(p);
    }

    /**
     * Access the next random variable using the given generator.
     * 
     * @param p the probability of success.
     * @param source the source generator.
     * @return the next random variable.
     */
    public static int nextRandomVariable(double p, RNG source) {
        return (p <= source.nextRandomNumber()) ? 1 : 0;
    }

    /**
     * Access the probability of success.
     * 
     * @return the probability of success.
     */
    private double getProbabilityOfSuccess() {
        return probabilityOfSuccess;
    }

    /**
     * Access the next random variable from this generator.
     * 
     * @return the next random variable.
     */
    public int nextRandomVariable() {
        return nextRandomVariable(getProbabilityOfSuccess(), getSource());
    }

    /**
     * Modify the probability of success.
     * 
     * @param p the new probability of success.
     */
    private void setProbabilityOfSuccess(double p) {
        if (Double.isNaN(p) || p <= 0.0 || p >= 1.0) {
            throw new IllegalArgumentException("probability of success must"
                + "be between 0.0 and 1.0, exclusive.");
        }
        this.probabilityOfSuccess = p;
    }

}