mathnet-numerics/examples/examples-csharp/SpecialFunctions/Factorial.cs

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using System;
using MathNet.Numerics;

namespace Examples.SpecialFunctionsExamples
{
    /// <summary>
    /// Special Functions: Factorial
    /// </summary>
    /// <seealso cref="http://reference.wolfram.com/mathematica/ref/Factorial.html"/>
    /// <seealso cref="http://reference.wolfram.com/mathematica/ref/Binomial.html"/>
    /// <seealso cref="http://reference.wolfram.com/mathematica/ref/Multinomial.html"/>
    public class Factorial : IExample
    {
        /// <summary>
        /// Gets the name of this example
        /// </summary>
        public string Name
        {
            get
            {
                return "Special Functions: Factorial";
            }
        }

        /// <summary>
        /// Gets the description of this example
        /// </summary>
        public string Description
        {
            get
            {
                return "Factorial, Binomial, Multinomial";
            }
        }

        /// <summary>
        /// Run example
        /// </summary>
        /// <seealso cref="http://en.wikipedia.org/wiki/Factorial">Factorial</seealso>
        /// <seealso cref="http://en.wikipedia.org/wiki/Binomial_coefficient">Binomial coefficient</seealso>
        /// <seealso cref="http://en.wikipedia.org/wiki/Multinomial_theorem#Multinomial_coefficients">Multinomial coefficients</seealso>
        public void Run()
        {
            // 1. Compute the factorial of 5
            Console.WriteLine(@"1. Compute the factorial of 5");
            Console.WriteLine(SpecialFunctions.Factorial(5).ToString("N"));
            Console.WriteLine();

            // 2. Compute the logarithm of the factorial of 5
            Console.WriteLine(@"2. Compute the logarithm of the factorial of 5");
            Console.WriteLine(SpecialFunctions.FactorialLn(5).ToString("N"));
            Console.WriteLine();

            // 3. Compute the binomial coefficient: 10 choose 8
            Console.WriteLine(@"3. Compute the binomial coefficient: 10 choose 8");
            Console.WriteLine(SpecialFunctions.Binomial(10, 8).ToString("N"));
            Console.WriteLine();

            // 4. Compute the logarithm of the binomial coefficient: 10 choose 8
            Console.WriteLine(@"4. Compute the logarithm of the binomial coefficient: 10 choose 8");
            Console.WriteLine(SpecialFunctions.BinomialLn(10, 8).ToString("N"));
            Console.WriteLine();

            // 5. Compute the multinomial coefficient: 10 choose 2, 3, 5 
            Console.WriteLine(@"5. Compute the multinomial coefficient: 10 choose 2, 3, 5");
            Console.WriteLine(SpecialFunctions.Multinomial(10, new[] { 2, 3, 5 }).ToString("N"));
            Console.WriteLine();
        }
    }
}