/// <summary>
/// Split the set according to a test.
/// </summary>
/// <param name="test"></param>
/// <returns></returns>
public override IEnumerable <ItemSet> Split(Test test)
{
WeightedItemSet[] sets = new WeightedItemSet[test.NumOfIssues];
double[] setSizes = new double[test.NumOfIssues];
double setSizeSum = 0.0d;
List <Item> unkonwnItems = new List <Item>();
List <double> unknownItemsWeights = new List <double>();
for (int i = 0; i < sets.Length; i++)
{
sets[i] = new WeightedItemSet(this._attributeSet);
}
for (int i = 0; i < this._items.Count; i++)
{
Item it = this._items[i];
double weight = this._weights[i];
AttributeValue val = it.ValueOf(this._attributeSet, test.Attribute);
if (val.IsUnknown())
{
unkonwnItems.Add(it);
unknownItemsWeights.Add(weight);
}
else
{
int id = test.Perform(val);
sets[id].Add(it, weight);
}
}
for (int i = 0; i < sets.Length; i++)
{
setSizes[i] = sets[i].Size();
setSizeSum += setSizes[i];
}
for (int i = 0; i < unkonwnItems.Count; i++)
{
Item it = unkonwnItems[i];
double weight = unknownItemsWeights[i];
for (int j = 0; j < sets.Length; j++)
{
sets[j].Add(it, weight * setSizes[j] / setSizeSum);
}
}
return(sets);
}
/// <summary>
/// Returns the distribution of goal values. This distributionis represented by an array,
/// its i-th element is proportional to the weight of the i-th goal value.
/// The Sum of the elements of this array is equal to 1.
/// </summary>
/// <returns>An array describing the goal value distribution associated to this node.</returns>
public override double[] GetGoalValueDistribution()
{
WeightedItemSet itemSet;
DecisionTree dt = base.Tree();
if (dt == null || _learningSet == null)
{
return(null);
}
if (!(_learningSet is WeightedItemSet))
{
itemSet = new WeightedItemSet(_learningSet);
}
else
{
itemSet = (WeightedItemSet)_learningSet;
}
SymbolicAttribute goalAttr = dt.GoalAttribute;
if (goalAttr == null)
{
return(null);
}
//Find the most frequent goal value in the items of the learning set
double[] frequencies = new double[goalAttr.NumOfValues];
for (int i = 0; i < itemSet.NumOfItems(); i++)
{
int id = ((KnownSymbolicValue)(itemSet.Items[i].ValueOf(itemSet.AttrSet.IndexOf(goalAttr)))).IntValue;
frequencies[id] += itemSet.GetWeight(i);
}
for (int i = 0; i < frequencies.Length; i++)
{
frequencies[i] /= itemSet.Size();
}
return(frequencies);
}
