Distributed probability random number generator

Question

I want to generate a number based on a distributed probability. For example, just say there are the following occurences of each numbers:

Number| Count               


        

Answer 1

Here's an implementation using the Inverse distribution function:

using System;
using System.Linq;

    // ...
    private static readonly Random RandomGenerator = new Random();

    private int GetDistributedRandomNumber()
    {
        double totalCount = 208;

        var number1Prob = 150 / totalCount;
        var number2Prob = (150 + 40) / totalCount;
        var number3Prob = (150 + 40 + 15) / totalCount;

        var randomNumber = RandomGenerator.NextDouble();

        int selectedNumber;

        if (randomNumber < number1Prob)
        {
            selectedNumber = 1;
        }
        else if (randomNumber >= number1Prob && randomNumber < number2Prob)
        {
            selectedNumber = 2;
        }
        else if (randomNumber >= number2Prob && randomNumber < number3Prob)
        {
            selectedNumber = 3;
        }
        else
        {
            selectedNumber = 4;
        }

        return selectedNumber;
    }

An example to verify the random distribution:

        int totalNumber1Count = 0;
        int totalNumber2Count = 0;
        int totalNumber3Count = 0;
        int totalNumber4Count = 0;

        int testTotalCount = 100;

        foreach (var unused in Enumerable.Range(1, testTotalCount))
        {
            int selectedNumber = GetDistributedRandomNumber();

            Console.WriteLine($"selected number is {selectedNumber}");

            if (selectedNumber == 1)
            {
                totalNumber1Count += 1;
            }

            if (selectedNumber == 2)
            {
                totalNumber2Count += 1;
            }

            if (selectedNumber == 3)
            {
                totalNumber3Count += 1;
            }

            if (selectedNumber == 4)
            {
                totalNumber4Count += 1;
            }
        }

        Console.WriteLine("");
        Console.WriteLine($"number 1 -> total selected count is {totalNumber1Count} ({100 * (totalNumber1Count / (double) testTotalCount):0.0} %) ");
        Console.WriteLine($"number 2 -> total selected count is {totalNumber2Count} ({100 * (totalNumber2Count / (double) testTotalCount):0.0} %) ");
        Console.WriteLine($"number 3 -> total selected count is {totalNumber3Count} ({100 * (totalNumber3Count / (double) testTotalCount):0.0} %) ");
        Console.WriteLine($"number 4 -> total selected count is {totalNumber4Count} ({100 * (totalNumber4Count / (double) testTotalCount):0.0} %) ");

Example output:

selected number is 1
selected number is 1
selected number is 1
selected number is 1
selected number is 2
selected number is 1
...
selected number is 2
selected number is 3
selected number is 1
selected number is 1
selected number is 1
selected number is 1
selected number is 1

number 1 -> total selected count is 71 (71.0 %) 
number 2 -> total selected count is 20 (20.0 %) 
number 3 -> total selected count is 8 (8.0 %) 
number 4 -> total selected count is 1 (1.0 %)