public void DiscreteChoiceFromCDF()
{
var r = new TMGRandom(12345);
var choiceModel = new DiscreteChoiceFromCDF()
{
Name = "Choice Model"
};
float[] data = Enumerable.Repeat(0f, 100).ToArray();
for (int i = 0; i < data.Length; i++)
{
data[i] = r.Pop();
}
var invSum = 1.0f / VectorHelper.Sum(data, 0, data.Length);
data[0] *= invSum;
for (int i = 1; i < data.Length; i++)
{
data[i] = (data[i] * invSum) + data[i - 1];
}
for (int i = 0; i < 100; i++)
{
var result = choiceModel.Invoke((r, data));
if (result < 0)
{
Assert.Fail("Generated a number less than zero!");
}
if (result >= data.Length)
{
Assert.Fail("Generated a number greater than the number of choices!");
}
}
}
public void DiscreteChoiceFromProbabilities()
{
var r = new TMGRandom(12345);
var choiceModel = new DiscreteChoiceFromProbabilities()
{
Name = "Choice Model"
};
float[] data = Enumerable.Repeat(0f, 100).ToArray();
for (int i = 0; i < data.Length; i++)
{
data[i] = r.Pop();
}
var total = VectorHelper.Sum(data, 0, data.Length);
VectorHelper.Multiply(data, data, 1.0f / total);
for (int i = 0; i < 100; i++)
{
var result = choiceModel.Invoke((r, data));
if (result < 0)
{
Assert.Fail("Generated a number less than zero!");
}
if (result >= data.Length)
{
Assert.Fail("Generated a number greater than the number of choices!");
}
}
}
/// <summary>
/// Randomly select an element from a CDF vector.
/// </summary>
/// <param name="random">The random algorithm to use.</param>
/// <param name="cdf">The CDF vector to chose from.</param>
/// <returns>The index that was selected.</returns>
public static int DiscreteChoiceFromCDF(TMGRandom random, Span <float> cdf)
{
var pop = random.Pop();
// there is no need to check the last element
for (int i = 0; i < cdf.Length - 1; i++)
{
if (pop > cdf[i])
{
return(i);
}
}
return(cdf.Length - 1);
}
/// <summary>
/// Randomly select an element from a probability vector.
/// </summary>
/// <param name="random">The random algorithm to use.</param>
/// <param name="probabilities">The probability vector to chose from.</param>
/// <returns>The index that was selected.</returns>
public static int DiscreteChoiceFromProbabilities(TMGRandom random, Span <float> probabilities)
{
var pop = random.Pop();
var acc = 0.0f;
for (int i = 0; i < probabilities.Length; i++)
{
acc += probabilities[i];
if (acc >= pop)
{
return(i);
}
}
return(probabilities.Length - 1);
}
