C# How to generate a random number in a range, biased toward the low end of the range?

Question

Helo! My code is:

    class Program
        {
            static void Main(string[] args)
            {
                for (int x = 0; x < 15000; x++)
                {
                    int minValue = 1;
                    int maxValue = 1400;
                var rand = new Random();

                List<float> weights = new List<float>();
                List<float> numbers = new List<float>();
                for (int i = minValue; i <= maxValue; i++)
                {
                    weights.Add((int)Math.Pow(i, 0.4));
                    numbers.Add(i);
                }
                weights.Reverse();

                int weightSum = 0;
                foreach (int weight in weights)
                {
                    weightSum += weight;
                }

                List<int> possibleNumberList = new List<int>();

                float randomNumber = rand.Next(minValue, weightSum);

                float leastDifference = 2000000000f;
                int leastDifferenceNumberIndex = -1;
                for (int weightIndex = 0; weightIndex < weights.Count - 1; weightIndex++)
                {
                    if (Math.Abs(weights[weightIndex] - randomNumber) == leastDifference)
                    {
                        leastDifference = Math.Abs(weights[weightIndex] - randomNumber);
                        leastDifferenceNumberIndex = weightIndex;

                        possibleNumberList.Add(weightIndex);
                    }
                    else if (Math.Abs(weights[weightIndex] - randomNumber) < leastDifference)
                    {
                        leastDifference = Math.Abs(weights[weightIndex] - randomNumber);
                        leastDifferenceNumberIndex = weightIndex;
                        possibleNumberList = new List<int>();
                        possibleNumberList.Add(weightIndex);
                    }
                }

                var randFromListR = new Random();

                int listCunt = possibleNumberList.Count;
                int index = randFromListR.Next(0, listCunt);
                WWriteStringToNewLine(possibleNumberList[index].ToString());
            }
        }
    }

My goal is to have a list or array shown in the image

Although my max value for me would be 1400.

With my code I can only achieve the following output:

If we zoom in, we can see that there are some higher numbers but generated only once.

If we set the code's max value to 10 the output is the following:

{3: 2837, 0: 2813, 4: 2781, 2: 2761, 1: 2759, 5: 273, 6: 264, 7: 262, 8: 250}

What could I change on this code to work correctly? What do you suggest? You can even give me a whole different code.

"Biased towards the lower end" this is very vague and can be achieved in a whole range of different ways (basic example would be to generate 2 random numbers and just return the lowest one). You then show a histogram but don't say if that's just an example of a distribution biased towards to lower end or if you want that exact distribution? (and would finding a formula fit be good enough or do you want to draw random numbers by sampling the provided histogram?) — , Nov 19 '20 at 08:59

score 1 · Answer 1 · answered Nov 19 '20 at 09:16

If you apply a function to your random result that will change your number repartition. I tried these : Exp(Random.Next(0,10000) / 100d) will generate a number with the repartition you apparently seek

Sqrt(Random.Next(0,10000)) will generate a number from 0 to 100 with a square root repartition.

You can take the integer part if needed

C# How to generate a random number in a range, biased toward the low end of the range?

1 Answers1