/// <summary>
/// Returns the element that is closest the the average of the values returned by the selector function.
/// </summary>
/// <typeparam name="TSource">The type of the elements of the source sequence.</typeparam>
/// <typeparam name="TSelector">The type of the element returned by the selector of the source sequence. TSelector must be numeric.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="selector">A function that return a numeric value used to evaluate the average sequence value.</param>
/// <param name="matchType">The type of matching to apply when seeking the closest item.</param>
/// <returns>The element that is closest the the average of the values returned by the selector function.</returns>
/// <remarks>Closest is defined by the match type.</remarks>
/// <exception cref="System.ArgumentNullException">source is null.</exception>
/// <exception cref="System.ArgumentNullException">selector is null.</exception>
/// <exception cref="System.ArgumentException">source must have one or more elements.</exception>
/// <exception cref="System.InvalidOperationException">Selector must return a numeric value.</exception>
public static TSource ElementAtAverage <TSource, TSelector>(this IEnumerable <TSource> source, Func <TSource, TSelector> selector, AverageMatchType matchType)
{
Helper.InvalidateNullParam(source, "source");
Helper.InvalidateNullParam(selector, "selector");
Helper.InvalidateEmptySequence(source, "source");
Helper.InvalidateNonNumeric <TSelector>("ElementAtAverage");
TSelector tempSum = default(TSelector);
int count = 0;
foreach (TSource item in source)
{
if (count == 0)
{
tempSum = selector(item);
count = 1;
continue;
}
tempSum = Arithmetic.Helper <TSelector> .Add(tempSum, selector(item));
count++;
}
decimal ts = Convert.ToDecimal(tempSum);
decimal tempAvg = ts / count;
TSource minElement = default(TSource);
TSource maxElement = default(TSource);
decimal minValue = 0;
decimal maxValue = 0;
bool firstMin = true;
bool firstMax = true;
foreach (TSource item in source)
{
decimal temp = Convert.ToDecimal(selector(item));
if (temp.CompareTo(tempAvg) <= 0)
{
if (firstMin || minValue.CompareTo(temp) <= 0)
{
firstMin = false;
minValue = temp;
minElement = item;
}
}
if (temp.CompareTo(tempAvg) >= 0)
{
if (firstMax || maxValue.CompareTo(temp) >= 0)
{
firstMax = false;
maxValue = temp;
maxElement = item;
}
}
}
decimal distanceOfMaxValue = maxValue - tempAvg;
decimal distanceOfMinValue = tempAvg - minValue;
switch (matchType)
{
case AverageMatchType.Exact:
if (distanceOfMaxValue == 0)
{
return(maxElement);
}
else
{
return(default(TSource));
}
case AverageMatchType.Closest:
if (distanceOfMaxValue < distanceOfMinValue)
{
return(maxElement);
}
else
{
return(minElement);
}
case AverageMatchType.ExactOrLarger:
return(maxElement);
case AverageMatchType.ExactOrSmaller:
return(minElement);
default:
throw new ArgumentOutOfRangeException("matchType", string.Format(Resources.exceptionMatchType, matchType));
}
}
/// <summary>
/// Returns the element that is closest the the average of the values returned by the selector function.
/// </summary>
/// <typeparam name="TSource">The type of the elements of the source sequence.</typeparam>
/// <typeparam name="TSelector">The type of the element returned by the selector of the source sequence. TSelector must be numeric.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="selector">A function that return a numeric value used to evaluate the average sequence value.</param>
/// <param name="matchType">The type of matching to apply when seeking the closest item.</param>
/// <returns>The element that is closest the the average of the values returned by the selector function.</returns>
/// <remarks>Closest is defined by the match type.</remarks>
/// <exception cref="System.ArgumentNullException">source is null.</exception>
/// <exception cref="System.ArgumentNullException">selector is null.</exception>
/// <exception cref="System.ArgumentException">source must have one or more elements.</exception>
/// <exception cref="System.InvalidOperationException">Selector must return a numeric value.</exception>
public static TSource ElementAtAverage <TSource, TSelector>(this IEnumerable <TSource> source, Func <TSource, TSelector> selector, AverageMatchType matchType)
{
if (source == null)
{
throw Error.ArgumentNull("source");
}
if (selector == null)
{
throw Error.ArgumentNull("selector");
}
TSource[] sourceArr = source.ToArray();
Helper.InvalidateEmptySequence(sourceArr, "source");
Helper.InvalidateNonNumeric <TSelector>("ElementAtAverage");
TSelector tempSum = default(TSelector);
int count = 0;
foreach (TSource item in sourceArr)
{
if (count == 0)
{
tempSum = selector(item);
count = 1;
continue;
}
tempSum = Arithmetic.Helper <TSelector> .Add(tempSum, selector(item));
count++;
}
decimal ts = Convert.ToDecimal(tempSum);
decimal tempAvg = ts / count;
TSource minElement = default(TSource);
TSource maxElement = default(TSource);
decimal minValue = 0;
decimal maxValue = 0;
bool firstMin = true;
bool firstMax = true;
foreach (TSource item in sourceArr)
{
decimal temp = Convert.ToDecimal(selector(item));
if (temp.CompareTo(tempAvg) <= 0)
{
if (firstMin || minValue.CompareTo(temp) <= 0)
{
firstMin = false;
minValue = temp;
minElement = item;
}
}
if (temp.CompareTo(tempAvg) >= 0)
{
if (firstMax || maxValue.CompareTo(temp) >= 0)
{
firstMax = false;
maxValue = temp;
maxElement = item;
}
}
}
decimal distanceOfMaxValue = maxValue - tempAvg;
decimal distanceOfMinValue = tempAvg - minValue;
switch (matchType)
{
case AverageMatchType.Exact:
if (distanceOfMaxValue == 0)
{
return(maxElement);
}
return(default(TSource));
case AverageMatchType.Closest:
if (distanceOfMaxValue < distanceOfMinValue)
{
return(maxElement);
}
return(minElement);
case AverageMatchType.ExactOrLarger:
return(maxElement);
case AverageMatchType.ExactOrSmaller:
return(minElement);
default:
throw Error.MatchType(matchType);
}
}
