BGC.Mathematics.Probability Class Reference

Static Public Member Functions
static int	GetIndexWIthPreviousLowerProbability (float arrayLength, int previousIndex)
	Get a random index from an array where the previous has a lower probability More...
static int	GetRandomIndexBasedOnWeights (float[] weights, bool verbose=false)
	Given an array of weights for each index of the array, return a random index based on said weights. More...

Detailed Description

Definition at line 6 of file Probability.cs.

Member Function Documentation

GetIndexWIthPreviousLowerProbability()

static int BGC.Mathematics.Probability.GetIndexWIthPreviousLowerProbability ( float  arrayLength, int  previousIndex  )

inlinestatic

Get a random index from an array where the previous has a lower probability

Definition at line 12 of file Probability.cs.

        {
            int index = -1;
            if (arrayLength <= 0)
            {   
                return index;
            }

            float regularProbability = 1f / arrayLength;
            float highProbability = 3f / (2f * arrayLength);
            float lowProbability = 1f / (2f * arrayLength);
            float lowSelectProbability = 1f / (arrayLength - 1f);

            float requriedProbForHighSelect = Random.value;
            float requiredProbForLowSelect  = Random.value;

            float cumulativeHighProbSelect = 0f;
            float cumulativeLowProbSelect  = 0f;

            bool lowProbabilitySelected = false;

            for (int i = 0; i < arrayLength; ++i)
            {
                if (i == previousIndex)
                {
                    cumulativeHighProbSelect += lowProbability;
                }
                else
                {
                    cumulativeLowProbSelect += lowSelectProbability;

                    if (lowProbabilitySelected && cumulativeLowProbSelect > requiredProbForLowSelect)
                    {
                        cumulativeHighProbSelect += highProbability;
                    }
                    else
                    {
                        cumulativeHighProbSelect += regularProbability;
                    }
                }

                if (cumulativeHighProbSelect > requriedProbForHighSelect)
                {
                    index = i;
                    break;
                }
            }

            if (index == -1)
            {
                index = ((int) arrayLength) - 1;
            }

            return index;
        }

GetRandomIndexBasedOnWeights()

static int BGC.Mathematics.Probability.GetRandomIndexBasedOnWeights ( float []  weights, bool  verbose = false  )

inlinestatic

Given an array of weights for each index of the array, return a random index based on said weights.

Definition at line 72 of file Probability.cs.

        {
            if (weights == null || weights.Length <= 0)
            {
                if (verbose && weights == null)
                {
                    Debug.LogError("Array is null and this function returned -1.");
                }
                else if (verbose)
                {
                    Debug.LogError("Array is <= 0 and this function returned -1.");
                }

                return -1;
            }

            int index   = 0;
            float total = 0;

            for (int i = 0; i < weights.Length; ++i)
            {
                total += weights[i];
            }

            if (total <= 0)
            {
                index = weights.RandomIndex();
            }
            else
            {
                float x = 1f / total;

                float random = Random.value;
                float cumulative = weights[0] * x;

                while (cumulative < random)
                {
                    ++index;
                    cumulative += weights[index] * x;
                }
            }

            return index;
        }

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The documentation for this class was generated from the following file:

• Mathematics/Probability.cs