/// <summary>
/// Calculates the marginal factors according to the marginal average tariff rating method.
/// </summary>
/// <returns>The mapping of each of the model's tariff attribute values to their marginal factors.</returns>
protected override IReadOnlyDictionary <TariffAttributeValue, decimal> CalculateFactors()
{
IDictionary <TariffAttributeValue, decimal> factors = new Dictionary <TariffAttributeValue, decimal>();
foreach (TariffAttributeValue tariffAttributeValue in TariffData.TariffKeys.SelectMany(x => x).Distinct())
{
decimal totalAmount = 0m;
int totalCount = 0;
foreach (TariffCell cell in TariffData[tariffAttributeValue])
{
totalAmount += cell.ClaimsAmount;
totalCount += cell.PolicyCount;
}
if (totalCount > 0)
{
factors[tariffAttributeValue] = (totalAmount / totalCount) / TariffData.ExpectedClaimsExpenditure();
}
else
{
factors[tariffAttributeValue] = 0m;
}
}
return(new ReadOnlyDictionary <TariffAttributeValue, decimal>(factors));
}
/// <summary>
/// Iteratively calculates the marginal factors for each attribute value.
/// </summary>
/// <param name="attributeValues">Attribute values the marginal factors are to be calculated for.</param>
/// <param name="factors">Starting values for the iterative calculation of the marginal factors.</param>
/// <returns>True if the threshold indicating a significant change in factors was undercut, false otherwise.</returns>
private bool CalculateFactorsIteratively(IEnumerable <TariffAttributeValue> attributeValues, ref IDictionary <TariffAttributeValue, decimal> factors)
{
bool thresholdReached = true;
foreach (TariffAttributeValue attributeValue in attributeValues)
{
IEnumerable <ITariffKey> keys = TariffData.TariffKeys.Where(x => x.Contains(attributeValue));
decimal aggregate = 0m;
foreach (ITariffKey key in keys)
{
decimal partialFactor = 1m;
foreach (TariffAttributeValue differentAttributeValue in key.Where(x => !x.Equals(attributeValue)))
{
partialFactor *= factors[differentAttributeValue];
}
aggregate += partialFactor * TariffData[key].PolicyCount;
}
decimal totalClaimsAmount = TariffData[attributeValue].Select(x => x.ClaimsAmount).Sum();
decimal factorAfterIteration = totalClaimsAmount / (TariffData.ExpectedClaimsExpenditure() * aggregate);
thresholdReached = thresholdReached && (Math.Abs(factorAfterIteration - factors[attributeValue]) < _deltaThreshold);
factors[attributeValue] = factorAfterIteration;
}
return(thresholdReached);
}
