public void TestEntropy()
{
Assert.AreEqual(1.4591, smallDistribution.Entropy(), 0.0001);
}
/**
* <summary> The DecisionNode method takes {@link InstanceList} data as input and then it sets the class label parameter by finding
* the most occurred class label of given data, it then gets distinct class labels as class labels List. Later, it adds ordered
* indices to the indexList and shuffles them randomly. Then, it gets the class distribution of given data and finds the best entropy value
* of these class distribution.
* <p/>
* If an attribute of given data is {@link DiscreteIndexedAttribute}, it creates a Distribution according to discrete indexed attribute class distribution
* and finds the entropy. If it is better than the last best entropy it reassigns the best entropy, best attribute and best split value according to
* the newly founded best entropy's index. At the end, it also add new distribution to the class distribution .
* <p/>
* If an attribute of given data is {@link DiscreteAttribute}, it directly finds the entropy. If it is better than the last best entropy it
* reassigns the best entropy, best attribute and best split value according to the newly founded best entropy's index.
* <p/>
* If an attribute of given data is {@link ContinuousAttribute}, it creates two distributions; left and right according to class distribution
* and discrete distribution respectively, and finds the entropy. If it is better than the last best entropy it reassigns the best entropy,
* best attribute and best split value according to the newly founded best entropy's index. At the end, it also add new distribution to
* the right distribution and removes from left distribution.</summary>
*
* <param name="data"> {@link InstanceList} input.</param>
* <param name="condition">{@link DecisionCondition} to check.</param>
* <param name="parameter">RandomForestParameter like seed, ensembleSize, attributeSubsetSize.</param>
* <param name="isStump"> Refers to decision trees with only 1 splitting rule.</param>
*/
public DecisionNode(InstanceList.InstanceList data, DecisionCondition condition,
RandomForestParameter parameter,
bool isStump)
{
int bestAttribute = -1, size;
double bestSplitValue = 0;
this._condition = condition;
this._data = data;
_classLabel = Classifier.Classifier.GetMaximum(data.GetClassLabels());
_leaf = true;
var classLabels = data.GetDistinctClassLabels();
if (classLabels.Count == 1)
{
return;
}
if (isStump && condition != null)
{
return;
}
var indexList = new List <int>();
for (var i = 0; i < data.Get(0).AttributeSize(); i++)
{
indexList.Add(i);
}
if (parameter != null && parameter.GetAttributeSubsetSize() < data.Get(0).AttributeSize())
{
size = parameter.GetAttributeSubsetSize();
}
else
{
size = data.Get(0).AttributeSize();
}
var classDistribution = data.ClassDistribution();
var bestEntropy = data.ClassDistribution().Entropy();
for (var j = 0; j < size; j++)
{
var index = indexList[j];
double entropy;
if (data.Get(0).GetAttribute(index) is DiscreteIndexedAttribute)
{
for (var k = 0; k < ((DiscreteIndexedAttribute)data.Get(0).GetAttribute(index)).GetMaxIndex(); k++)
{
var distribution = data.DiscreteIndexedAttributeClassDistribution(index, k);
if (distribution.GetSum() > 0)
{
classDistribution.RemoveDistribution(distribution);
entropy = (classDistribution.Entropy() * classDistribution.GetSum() +
distribution.Entropy() * distribution.GetSum()) / data.Size();
if (entropy < bestEntropy)
{
bestEntropy = entropy;
bestAttribute = index;
bestSplitValue = k;
}
classDistribution.AddDistribution(distribution);
}
}
}
else
{
if (data.Get(0).GetAttribute(index) is DiscreteAttribute)
{
entropy = EntropyForDiscreteAttribute(index);
if (entropy < bestEntropy)
{
bestEntropy = entropy;
bestAttribute = index;
}
}
else
{
if (data.Get(0).GetAttribute(index) is ContinuousAttribute)
{
data.Sort(index);
var previousValue = double.MinValue;
var leftDistribution = data.ClassDistribution();
var rightDistribution = new DiscreteDistribution();
for (var k = 0; k < data.Size(); k++)
{
var instance = data.Get(k);
if (k == 0)
{
previousValue = ((ContinuousAttribute)instance.GetAttribute(index)).GetValue();
}
else
{
if (((ContinuousAttribute)instance.GetAttribute(index)).GetValue() !=
previousValue)
{
var splitValue =
(previousValue + ((ContinuousAttribute)instance.GetAttribute(index))
.GetValue()) / 2;
previousValue = ((ContinuousAttribute)instance.GetAttribute(index)).GetValue();
entropy =
(leftDistribution.GetSum() / data.Size()) * leftDistribution.Entropy() +
(rightDistribution.GetSum() / data.Size()) * rightDistribution.Entropy();
if (entropy < bestEntropy)
{
bestEntropy = entropy;
bestSplitValue = splitValue;
bestAttribute = index;
}
}
}
leftDistribution.RemoveItem(instance.GetClassLabel());
rightDistribution.AddItem(instance.GetClassLabel());
}
}
}
}
}
if (bestAttribute != -1)
{
_leaf = false;
if (data.Get(0).GetAttribute(bestAttribute) is DiscreteIndexedAttribute)
{
CreateChildrenForDiscreteIndexed(bestAttribute, (int)bestSplitValue, parameter, isStump);
}
else
{
if (data.Get(0).GetAttribute(bestAttribute) is DiscreteAttribute)
{
CreateChildrenForDiscrete(bestAttribute, parameter, isStump);
}
else
{
if (data.Get(0).GetAttribute(bestAttribute) is ContinuousAttribute)
{
CreateChildrenForContinuous(bestAttribute, bestSplitValue, parameter, isStump);
}
}
}
}
}