C#产生正态分布、泊松分布、指数分布、负指数分布随机数（原创）_c#正态分布随机数

http://blog.sina.com.cn/s/blog_76c31b8e0100qskf.html

在编程过程中，由于数据仿真模拟的需要，我们经常需要产生一些随机数，在C#中，产生一般随机数用Random即可，但是，若要产生服从特定分布的随机数，就需要一定的算法来支持了，为了方便广大编程人员，我将我再做项目过程中用到的产生服从正态分布、泊松分布、指数分布以及负指数分布随机数的方法与大家共享，希望会有所帮助！

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;

namespace PZ
{
    class Model
    {
        /// <summary>
        /// 正态分布随机数
        /// </summary>
        const int N = 100;
        const int MAX = 50;
        const double MIN = 0.1;
        const int MIU = 40;
        const int SIGMA = 1;
        static Random aa = new Random((int)(DateTime.Now.Ticks / 10000));
        public double AverageRandom(double min, double max)//产生(min,max)之间均匀分布的随机数
        {
            int MINnteger = (int)(min * 10000);
            int MAXnteger = (int)(max * 10000);
            int resultInteger = aa.Next(MINnteger, MAXnteger);
            return resultInteger / 10000.0;
        }
        public double Normal(double x, double miu, double sigma) //正态分布概率密度函数
        {
            return 1.0 / (x * Math.Sqrt(2 * Math.PI) * sigma) * Math.Exp(-1 * (Math.Log(x) - miu) * (Math.Log(x) - miu) / (2 * sigma * sigma));
        }
        public double Random_Normal(double miu, double sigma, double min, double max)//产生正态分布随机数
        {
            double x;
            double dScope;
            double y;
            do
            {
                x = AverageRandom(min, max);
                y = Normal(x, miu, sigma);
                dScope = AverageRandom(0, Normal(miu, miu, sigma));
            } while (dScope > y);
            return x;
        }

        /// <summary>
        /// 指数分布随机数
        /// </summary>
        /// <param name="const_a"></param>
        /// <returns></returns>
        public  double RandExp(double const_a)//const_a是指数分布的参数λ
        {
            Random rand = new Random(Guid.NewGuid().GetHashCode());
            double p;
            double temp;
            if (const_a != 0)
                temp = 1 / const_a;
            else
                throw new System.InvalidOperationException("除数不能为零！不能产生参数为零的指数分布！");
            double randres;
            while (true) //用于产生随机的密度，保证比参数λ小
            {
                p = rand.NextDouble();
                if (p < const_a)
                    break;
            }
            randres = -temp * Math.Log(temp * p, Math.E);
            return randres;
        }

        /// <summary>
        /// 负指数分布随机数产生
        /// </summary>
        /// <param name="lam">参数</param>
        /// <returns></returns>
        Random ran;

        public Model()
        {
            ran = new Random();
        }
        public double ngtIndex(double lam)
        {
            double dec = ran.NextDouble();
            while (dec == 0)
                dec = ran.NextDouble();
            return -Math.Log(dec) / lam;
        }

        /// <summary>
        /// 泊松分布产生
        /// </summary>
        /// <param name="lam">参数</param>
        /// <param name="time">时间</param>
        /// <returns></returns>
        public double poisson(double lam, double time)
        {
            int count = 0;

            while (true)
            {
                time -= ngtIndex(lam);
                if (time > 0)
                    count++;
                else
                    break;
            }
            return count;
        }
 
        }

    }