//////////////////////////////////////////////////////
// Function:
// Classify
//
// Purpose:
// Returns the classification of the given data.
//
// Note:
// Data is given as an example object, but the
// classification calculated is not placed
// into the query object.
//////////////////////////////////////////////////////
public override string Classify(
CClassificationData inQuery)
{
var szOutClassification = "UNKNOWN";
CDTNode pNodeToInspect = new CDTNode(m_decisionTreeRootNode);
while (pNodeToInspect != null)
{
int iChildCount = pNodeToInspect.GetChildren().Count();
if (iChildCount == 0)
{
szOutClassification = m_rwClasses[pNodeToInspect.GetClassIdentifier()];
break;
}
else
{
int iAttributeID = pNodeToInspect.GetAttributeIdentifier();
int iValueID = inQuery.GetValueIdentifier(iAttributeID);
pNodeToInspect = pNodeToInspect.GetChildren()[iValueID];
}
}
return(szOutClassification);
}
public CDTNode(CDTNode inOtherNode)
{
m_pDecisionTree = inOtherNode.m_pDecisionTree;
m_fEntropy = inOtherNode.m_fEntropy;
m_iClass = inOtherNode.m_iClass;
m_bIsLeaf = inOtherNode.m_bIsLeaf;
m_rwRemainingAttributeIDs = inOtherNode.m_rwRemainingAttributeIDs;
m_rwExampleIDs = inOtherNode.m_rwExampleIDs;
m_rwChildren = inOtherNode.m_rwChildren;
m_rwInformationGain = inOtherNode.m_rwInformationGain;
m_iAttributeID = inOtherNode.m_iAttributeID;
m_rwClassCount = inOtherNode.m_rwClassCount;
}
public CDecisionTree()
{
m_decisionTreeRootNode = new CDTNode();
}
//////////////////////////////////////////////////////
// Mutator:
// CDTNode::Train
//
// Purpose:
// Calculates the information gain for the remaining
// attributes, the entropy of the remaining examples
// and creates splits/sub-nodes
//////////////////////////////////////////////////////
public void Train()
{
// Note:
// I need a better approach to situations where noe more attributes
// are left to split on, but multiple classes exist in the examples.
// If we don't have any examples to train on, then
// this node HAS to be a leaf. We will keep the classification
// given to us which was the most common class from the parent node
if (m_rwExampleIDs.Count() == 0)
{
m_bIsLeaf = true;
return;
}
m_bIsLeaf = false;
m_fEntropy = GetEntropy();
//assert( m_fEntropy >= 0.0f );
//assert( m_fEntropy <= ( (float)m_pDecisionTree->GetNumClasses() - 1.0f ) );
// If we don't have any entropy, then go ahead and treat this like a leaf
// since we don't have any reason to calculate any more
if (m_fEntropy == 0.0f)
{
m_bIsLeaf = true;
m_iClass = m_pDecisionTree.GetExample(m_rwExampleIDs[0]).GetClassIdentifier();
return;
}
// Calculate the gains for the attributes
int iAttributeID = 0;
int i = 0;
int iBestClassCount = 0; // The number of times the most common class appears
int iBestAttributeID = m_rwRemainingAttributeIDs[0]; // Treat the first attribute initially as the best
float fBestGain = GetInformationGain(iBestAttributeID); // Save the information gain from the first attribute
m_rwInformationGain = new List <float>();
for (i = 0; i < m_pDecisionTree.GetNumAttributes(); ++i)
{
m_rwInformationGain.Add(0.0f);
}
// Put the gain we just calculated into the proper place
m_rwInformationGain[iBestAttributeID] = fBestGain;
// Find the information gain for each attribute and store it
// while keeping track of the best gain and the attribute
// that it goes with.
int iRemainingAttributeCount = m_rwRemainingAttributeIDs.Count();
for (i = 1; i < iRemainingAttributeCount; ++i)
{
iAttributeID = m_rwRemainingAttributeIDs[i];
m_rwInformationGain[iAttributeID] = GetInformationGain(iAttributeID);
// If we find a better gain, store it
// and remember which attribute it came from
if (m_rwInformationGain[iAttributeID] > fBestGain)
{
fBestGain = m_rwInformationGain[iAttributeID];
iBestAttributeID = iAttributeID;
}
}
// Set the class counts to 0
m_rwClassCount = new List <int>();
int iTreeClassCount = m_pDecisionTree.GetNumClasses();
for (i = 0; i < iTreeClassCount; ++i)
{
m_rwClassCount.Add(0);
}
// Store the attribute this splits on
m_iAttributeID = iBestAttributeID;
// Modify the list of attributes to give to the new children
List <int> rwNewAttributeList = m_rwRemainingAttributeIDs;
// If we don't have any attributes left to split on
// then this node has to be a leaf, so we need to
// find the most common class for the examples
// and make that the node's classification
m_bIsLeaf = !m_rwRemainingAttributeIDs.Any();
// If we are not a leaf, then generate the children nodes
// and give them a list of remaining attributes they can split on
if (!m_bIsLeaf)
{
rwNewAttributeList = (from attributeId in rwNewAttributeList where attributeId != m_iAttributeID select attributeId).ToList();
// Create the sub-nodes
CAttribute attributeToSplitOn = m_pDecisionTree.GetAttribute(m_iAttributeID);
int iAttributeValueCount = attributeToSplitOn.GetNumValues();
for (i = 0; i < iAttributeValueCount; ++i)
{
CDTNode pNewNode = new CDTNode(m_pDecisionTree, rwNewAttributeList);
m_rwChildren.Add(pNewNode);
}
}
// Now we know the best attribute to split/branch on
// send the examples to their appropriate child nodes
// while finding the most common classification
// for this node's examples
int iExampleCount = m_rwExampleIDs.Count();
for (i = 0; i < iExampleCount; ++i)
{
int iExampleID = m_rwExampleIDs[i];
CExample curExample = m_pDecisionTree.GetExample(iExampleID);
int iExampleClassID = curExample.GetClassIdentifier();
// Save a tally of the occurrence of each classification
// and which class is the most common
++m_rwClassCount[iExampleClassID];
if (iBestClassCount < m_rwClassCount[iExampleClassID])
{
iBestClassCount = m_rwClassCount[iExampleClassID];
m_iClass = iExampleClassID;
}
// Match the examples with the sub tree that matches the attribute's value
if (!m_bIsLeaf)
{
int iValueID = curExample.GetValueIdentifier(m_iAttributeID);
// Add the example into the correct sub-tree and remove it from this level
m_rwChildren[iValueID].GetExampleIdentifierList().Add(iExampleID);
}
}
// If we are a leaf, then we don't have any children
// nodes to calculate so just return back
if (m_bIsLeaf)
{
return;
}
// No more examples should be associated with this node.
m_rwExampleIDs.Clear();
// Calculate all the subtrees for this node
int iNumValues = m_pDecisionTree.GetAttribute(m_iAttributeID).GetNumValues();
for (i = 0; i < iNumValues; ++i)
{
m_rwChildren[i].m_iClass = m_iClass;
m_rwChildren[i].Train();
}
}
//////////////////////////////////////////////////////
// Function:
// LoadFromFile
//
// Purpose:
// Loads the node from the given IO file.
// Returns FALSE in case of error.
//////////////////////////////////////////////////////
public bool LoadFromFile(
StreamReader pInInputFile)
{
m_iClass = 0;
m_iAttributeID = 0;
m_fEntropy = 0.0f;
m_rwInformationGain.Clear();
m_rwExampleIDs.Clear();
m_rwChildren.Clear();
string inputLine = pInInputFile.ReadLine().Trim();
string[] tokens = inputLine.Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
if (tokens == null || tokens.Length != 2)
{
return(false);
}
string szNodeType = tokens[0].Trim();
string szAttributeName = tokens[1].Trim();
if (string.Compare(m_szSplitKeyword, szNodeType, StringComparison.InvariantCultureIgnoreCase) == 0)
{
int iAttributeIdentifier = 0;
if (m_pDecisionTree.GetAttributeIdentifier(szAttributeName, ref iAttributeIdentifier))
{
int iNumChildren = m_pDecisionTree.GetAttribute(iAttributeIdentifier).GetNumValues();
m_iAttributeID = iAttributeIdentifier;
int iChildIndex = 0;
// Create the data first since we could read the
// tree in an arbitrary order..
for (iChildIndex = 0; iChildIndex < iNumChildren; ++iChildIndex)
{
var pNewNode = new CDTNode();
if (pNewNode == null)
{
return(false);
}
pNewNode.SetDecisionTree(m_pDecisionTree);
m_rwChildren.Add(pNewNode);
}
m_bIsLeaf = false;
}
else
{
return(false);
}
foreach (CDTNode pLinkNode in m_rwChildren)
{
string szAttributeValue = pInInputFile.ReadLine().Trim();
int iValueIdentifer = 0;
if (m_pDecisionTree.GetAttribute(m_iAttributeID).GetValueIdentifier(szAttributeValue, ref iValueIdentifer))
{
pLinkNode.LoadFromFile(pInInputFile);
}
else
{
return(false);
}
}
}
else if (m_szOutcomeKeyword == szNodeType)
{
// Leaf in tree
int iClassIdentifier = 0;
m_bIsLeaf = true;
if (m_pDecisionTree.GetClassIdentifier(szAttributeName, ref iClassIdentifier))
{
m_iClass = iClassIdentifier;
}
else
{
return(false);
}
}
else
{
// Unexpected input
return(false);
}
return(true);
}
