/// <summary>
/// Calculates the truncated mean of the specified collection of numbers
/// regarding the specified percentage of elements to be discarded.
/// </summary>
/// <param name="numbers">The numbers whose truncated mean is to be calculated.</param>
/// <param name="percentageToDiscard">The percentage of elements that
/// are to be discarded at both sides of the collection in each case.</param>
/// <returns>The truncated mean of the specified collection of numbers.</returns>
/// <exception cref="System.InvalidOperationException">
/// The specified collection must not be empty.
/// </exception>
/// <exception cref="System.ArgumentNullException">
/// The specified collection must not be null.
/// </exception>
public static double TruncatedMean(IEnumerable <double> numbers,
double percentageToDiscard)
{
if (numbers == null)
{
throw ArgumentNullException;
}
if (!numbers.Any())
{
throw EmptyNumbersCollectionException;
}
// The percentage to discard needs to be greater than 0 and smaller than 50% as
// it makes no sense to both discard nothing and discard all (50% on both sides).
if (percentageToDiscard <= 0 ||
percentageToDiscard >= 0.5)
{
throw new ArgumentException(
"percentageToDiscard must be greater than 0 and smaller than 0.5!");
}
var orderedNumbers = numbers.OrderBy(n => n);
IEnumerable <double> truncatedNumbers =
TruncationHelper <double> .Truncate(orderedNumbers, percentageToDiscard);
double truncatedMean = truncatedNumbers.ArithmeticMean();
return(truncatedMean);
}
/// <summary>
/// Calculates the winsorized mean of the specified collection of numbers
/// regarding the specified percentage of elements to be replaced.
/// </summary>
/// <param name="numbers">The numbers whose winsorized mean is to be calculated.</param>
/// <param name="percentageToReplace">The percentage to replace.</param>
/// <returns>
/// The winsorized mean of the specified collection of numbers.
/// </returns>
/// <exception cref="System.InvalidOperationException">
/// The specified collection must not be empty.
/// </exception>
/// <exception cref="System.ArgumentNullException">
/// The specified collection must not be null.
/// </exception>
/// <exception cref="System.ArgumentNullException">
/// The specified percentage to replace must be greater than zero and smaller than 0.5.
/// </exception>
public static double WinsorizedMean(IEnumerable <double> numbers,
double percentageToReplace)
{
if (numbers == null)
{
throw ArgumentNullException;
}
if (!numbers.Any())
{
throw EmptyNumbersCollectionException;
}
// The percentage to replace needs to be greater than 0 and smaller than 50% as
// it makes no sense to both replace nothing and replace all (50% on both sides).
if (percentageToReplace <= 0 ||
percentageToReplace >= 0.5)
{
throw new ArgumentException(
"percentageToReplace must be greater than 0 and smaller than 0.5!");
}
var orderedNumbers = numbers.OrderBy(n => n);
List <double> truncatedNumbers =
TruncationHelper <double> .Truncate(orderedNumbers, percentageToReplace)
.ToList();
int numberOfElements = numbers.Count();
int elementsToReplace = (int)Math.Floor(numberOfElements * percentageToReplace);
double minValue = truncatedNumbers.Min();
double maxValue = truncatedNumbers.Max();
for (int i = 0; i < elementsToReplace; i++)
{
truncatedNumbers.Insert(0, minValue);
truncatedNumbers.Add(maxValue);
}
double winsorizedMean = truncatedNumbers.ArithmeticMean();
return(winsorizedMean);
}
