jube-fork/Accord.Statistics/Distributions/Univariate/Continuous/RademacherDistribution.cs

// Accord Statistics Library
// The Accord.NET Framework
// http://accord-framework.net
//
// Copyright © César Souza, 2009-2017
// cesarsouza at gmail.com
//
//    This library is free software; you can redistribute it and/or
//    modify it under the terms of the GNU Lesser General Public
//    License as published by the Free Software Foundation; either
//    version 2.1 of the License, or (at your option) any later version.
//
//    This library is distributed in the hope that it will be useful,
//    but WITHOUT ANY WARRANTY; without even the implied warranty of
//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
//    Lesser General Public License for more details.
//
//    You should have received a copy of the GNU Lesser General Public
//    License along with this library; if not, write to the Free Software
//    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
//

namespace Accord.Statistics.Distributions.Univariate
{
    using System;

    /// <summary>
    ///   Rademacher distribution.
    /// </summary>
    /// 
    public class RademacherDistribution : UnivariateDiscreteDistribution
    {
        /// <summary>
        ///   Gets the mean for this distribution.
        /// </summary>
        /// 
        /// <value>
        ///   The distribution's mean value.
        /// </value>
        /// 
        public override double Mean
        {
            get { return 0; }
            set {} //Not Implemented.
        }

        /// <summary>
        ///   Gets the variance for this distribution.
        /// </summary>
        /// 
        /// <value>
        ///   The distribution's variance.
        /// </value>
        /// 
        public override double Variance
        {
            get { return 1; }
            set {} //Not Implemented.
        }

        /// <summary>
        /// Gets the median for this distribution.
        /// </summary>
        /// <value>The distribution's median value.</value>
        public override double Median
        {
            get { return 0; }
        }

        /// <summary>
        ///   Gets the entropy for this distribution.
        /// </summary>
        /// 
        /// <value>
        ///   The distribution's entropy.
        /// </value>
        /// 
        public override double Entropy
        {
            get { return System.Math.Log(2); }
            set {} //Not Implemented.
        }

        /// <summary>
        ///   Returns NaN.
        /// </summary>
        /// 
        public override double Mode
        {
            get { return Double.NaN; }
            set { } //Not Implemented.
        }

        /// <summary>
        ///   Gets the support interval for this distribution.
        /// </summary>
        /// 
        /// <value>
        ///   A <see cref="IntRange" /> containing
        ///   the support interval for this distribution.
        /// </value>
        /// 
        public override IntRange Support
        {
            get { return new IntRange(-1, +1); }
        }

        /// <summary>
        ///   Gets P(X ≤ k), the cumulative distribution function
        ///   (cdf) for this distribution evaluated at point <c>k</c>.
        /// </summary>
        /// 
        /// <param name="k">A single point in the distribution range.</param>
        /// 
        /// <remarks>
        ///   The Cumulative Distribution Function (CDF) describes the cumulative
        ///   probability that a given value or any value smaller than it will occur.
        /// </remarks>
        /// 
        protected internal override double InnerDistributionFunction(int k)
        {
            return 0.5;
        }

        /// <summary>
        ///   Gets the probability mass function (pmf) for
        ///   this distribution evaluated at point <c>x</c>.
        /// </summary>
        /// 
        /// <param name="k">A single point in the distribution range.</param>
        /// 
        /// <returns>
        ///   The probability of <c>k</c> occurring
        ///   in the current distribution.
        /// </returns>
        /// 
        /// <remarks>
        ///   The Probability Mass Function (PMF) describes the
        ///   probability that a given value <c>x</c> will occur.
        /// </remarks>
        /// 
        protected internal override double InnerProbabilityMassFunction(int k)
        {
            if (k == -1)
                return 0.5;
            if (k == +1)
                return 0.5;
            return 0.0;
        }

        /// <summary>
        ///   Returns a <see cref="System.String" /> that represents this instance.
        /// </summary>
        /// 
        /// <param name="format">The format.</param>
        /// <param name="formatProvider">The format provider.</param>
        /// 
        /// <returns>
        ///   A <see cref="System.String" /> that represents this instance.
        /// </returns>
        /// 
        public override string ToString(string format, IFormatProvider formatProvider)
        {
            return "Rademacher(x)";
        }

        /// <summary>
        ///   Creates a new object that is a copy of the current instance.
        /// </summary>
        /// 
        /// <returns>
        ///   A new object that is a copy of this instance.
        /// </returns>
        /// 
        public override object Clone()
        {
            return new RademacherDistribution();
        }
    }
}