/**
* Calculates the centroid pivot of a node based on the list of points that it contains (tbe two
* lists of its children are provided).
*
* @param list1 The point index list of first child.
* @param list2 The point index list of second child.
* @param insts The insts object on which the tree is being built (for header information).
* @return The centroid pivot of the node.
*/
public Instance calcPivot(MyIdxList list1, MyIdxList list2, Instances insts) {
int classIdx = m_Instances.classIndex();
double[] attrVals = new double[insts.numAttributes()];
Instance temp;
for (int i = 0; i < list1.length(); i++) {
temp = insts.instance(((ListNode) list1.get(i)).idx);
for (int k = 0; k < temp.numValues(); k++) {
if (temp.index(k) == classIdx) continue;
attrVals[k] += temp.valueSparse(k);
}
}
for (int j = 0; j < list2.length(); j++) {
temp = insts.instance(((ListNode) list2.get(j)).idx);
for (int k = 0; k < temp.numValues(); k++) {
if (temp.index(k) == classIdx) continue;
attrVals[k] += temp.valueSparse(k);
}
}
for (int j = 0, numInsts = list1.length() + list2.length(); j < attrVals.length; j++) {
attrVals[j] /= numInsts;
}
temp = new DenseInstance(1.0, attrVals);
return temp;
}
/**
* Compute the MI between instances and attributes
*
* @param m the term-document matrix
* @param input object that describes the statistics about the training data
*/
private void MI(Matrix m, Input input) {
int minDimSize =
m.getColumnDimension() < m.getRowDimension() ? m.getColumnDimension() : m.getRowDimension();
if (minDimSize < 2) {
System.err.println("Warning : This is not a JOINT distribution");
input.Hx = Entropy(m);
input.Hy = 0;
input.Ixy = 0;
return;
}
input.Hx = Entropy(input.Px);
input.Hy = Entropy(input.Py);
double entropy = input.Hx + input.Hy;
for (int i = 0; i < m_numInstances; i++) {
Instance inst = m_data.instance(i);
for (int v = 0; v < inst.numValues(); v++) {
double tmp = m.get(inst.index(v), i);
if (tmp <= 0) {
continue;
}
entropy += tmp * Math.log(tmp);
}
}
input.Ixy = entropy;
if (m_verbose) {
System.out.println("Ixy = " + input.Ixy);
}
}
/**
* @param inst
* @return
* @throws Exception
*/
public double SVMOutput(Instance inst) throws Exception {
double result = -m_b;
// Is the machine linear?
if (m_weights != null) {
// Is weight vector stored in sparse format?
for (int i = 0; i < inst.numValues(); i++) {
if (inst.index(i) != m_classIndex) {
result += m_weights[inst.index(i)] * inst.valueSparse(i);
}
}
} else {
for (int i = m_supportVectors.getNext(-1); i != -1; i = m_supportVectors.getNext(i)) {
result += (m_alpha[i] - m_alphaStar[i]) * m_kernel.eval(-1, i, inst);
}
}
return result;
}
/**
* Transpose the document-term matrix to term-document matrix
*
* @param data instances with document-term info
* @return a term-document matrix transposed from the input dataset
*/
private Matrix getTransposedMatrix(Instances data) {
double[][] temp = new double[data.numAttributes()][data.numInstances()];
for (int i = 0; i < data.numInstances(); i++) {
Instance inst = data.instance(i);
for (int v = 0; v < inst.numValues(); v++) {
temp[inst.index(v)][i] = inst.valueSparse(v);
}
}
Matrix My_x = new Matrix(temp);
return My_x;
}
/**
* Calculates the distance between two instances
*
* @param test the first instance
* @param train the second instance
* @return the distance between the two given instances, between 0 and 1
*/
protected double distance(Instance first, Instance second) {
double distance = 0;
int firstI, secondI;
for (int p1 = 0, p2 = 0; p1 < first.numValues() || p2 < second.numValues(); ) {
if (p1 >= first.numValues()) {
firstI = m_instances.numAttributes();
} else {
firstI = first.index(p1);
}
if (p2 >= second.numValues()) {
secondI = m_instances.numAttributes();
} else {
secondI = second.index(p2);
}
if (firstI == m_instances.classIndex()) {
p1++;
continue;
}
if (secondI == m_instances.classIndex()) {
p2++;
continue;
}
double diff;
if (firstI == secondI) {
diff = difference(firstI, first.valueSparse(p1), second.valueSparse(p2));
p1++;
p2++;
} else if (firstI > secondI) {
diff = difference(secondI, 0, second.valueSparse(p2));
p2++;
} else {
diff = difference(firstI, first.valueSparse(p1), 0);
p1++;
}
distance += diff * diff;
}
return Math.sqrt(distance / m_instances.numAttributes());
}
/**
* log(N!) + (for all the words)(log(Pi^ni) - log(ni!))
*
* <p>where N is the total number of words Pi is the probability of obtaining word i ni is the
* number of times the word at index i occurs in the document
*
* @param inst The instance to be classified
* @param classIndex The index of the class we are calculating the probability with respect to
* @return The log of the probability of the document occuring given the class
*/
private double probOfDocGivenClass(Instance inst, int classIndex) {
double answer = 0;
// double totalWords = 0; //no need as we are not calculating the factorial at all.
double freqOfWordInDoc; // should be double
for (int i = 0; i < inst.numValues(); i++)
if (inst.index(i) != inst.classIndex()) {
freqOfWordInDoc = inst.valueSparse(i);
// totalWords += freqOfWordInDoc;
answer +=
(freqOfWordInDoc
* m_probOfWordGivenClass[classIndex][
inst.index(i)]); // - lnFactorial(freqOfWordInDoc));
}
// answer += lnFactorial(totalWords);//The factorial terms don't make
// any difference to the classifier's
// accuracy, so not needed.
return answer;
}
/**
* Compute the JS divergence between an instance and a cluster, used for training data
*
* @param instIdx index of the instance
* @param input statistics of the input data
* @param T the whole partition
* @param t index of the cluster
* @param pi1
* @param pi2
* @return the JS divergence
*/
private double JS(int instIdx, Input input, Partition T, int t, double pi1, double pi2) {
if (Math.min(pi1, pi2) <= 0) {
System.out.format(
"Warning: zero or negative weights in JS calculation! (pi1 %s, pi2 %s)\n", pi1, pi2);
return 0;
}
Instance inst = m_data.instance(instIdx);
double kl1 = 0.0, kl2 = 0.0, tmp = 0.0;
for (int i = 0; i < inst.numValues(); i++) {
tmp = input.Py_x.get(inst.index(i), instIdx);
if (tmp != 0) {
kl1 += tmp * Math.log(tmp / (tmp * pi1 + pi2 * T.Py_t.get(inst.index(i), t)));
}
}
for (int i = 0; i < m_numAttributes; i++) {
if ((tmp = T.Py_t.get(i, t)) != 0) {
kl2 += tmp * Math.log(tmp / (input.Py_x.get(i, instIdx) * pi1 + pi2 * tmp));
}
}
return pi1 * kl1 + pi2 * kl2;
}
/**
* Checks if an instance contains an item set.
*
* @param instance the instance to be tested
* @return true if the given instance contains this item set
*/
public boolean containedByTreatZeroAsMissing(Instance instance) {
if (instance instanceof weka.core.SparseInstance) {
int numInstVals = instance.numValues();
int numItemSetVals = m_items.length;
for (int p1 = 0, p2 = 0; p1 < numInstVals || p2 < numItemSetVals; ) {
int instIndex = Integer.MAX_VALUE;
if (p1 < numInstVals) {
instIndex = instance.index(p1);
}
int itemIndex = p2;
if (m_items[itemIndex] > -1) {
if (itemIndex != instIndex) {
return false;
} else {
if (instance.isMissingSparse(p1)) {
return false;
}
if (m_items[itemIndex] != (int) instance.valueSparse(p1)) {
return false;
}
}
p1++;
p2++;
} else {
if (itemIndex < instIndex) {
p2++;
} else if (itemIndex == instIndex) {
p2++;
p1++;
}
}
}
} else {
for (int i = 0; i < instance.numAttributes(); i++) {
if (m_items[i] > -1) {
if (instance.isMissing(i) || (int) instance.value(i) == 0) {
return false;
}
if (m_items[i] != (int) instance.value(i)) {
return false;
}
}
}
}
return true;
}
/**
* Compute the JS divergence between an instance and a cluster, used for test data
*
* @param inst instance to be clustered
* @param t index of the cluster
* @param pi1
* @param pi2
* @return the JS divergence
*/
private double JS(Instance inst, int t, double pi1, double pi2) {
if (Math.min(pi1, pi2) <= 0) {
System.out.format(
"Warning: zero or negative weights in JS calculation! (pi1 %s, pi2 %s)\n", pi1, pi2);
return 0;
}
double sum = Utils.sum(inst.toDoubleArray());
double kl1 = 0.0, kl2 = 0.0, tmp = 0.0;
for (int i = 0; i < inst.numValues(); i++) {
tmp = inst.valueSparse(i) / sum;
if (tmp != 0) {
kl1 += tmp * Math.log(tmp / (tmp * pi1 + pi2 * bestT.Py_t.get(inst.index(i), t)));
}
}
for (int i = 0; i < m_numAttributes; i++) {
if ((tmp = bestT.Py_t.get(i, t)) != 0) {
kl2 += tmp * Math.log(tmp / (inst.value(i) * pi1 / sum + pi2 * tmp));
}
}
return pi1 * kl1 + pi2 * kl2;
}
/**
* Generates the classifier.
*
* @param instances set of instances serving as training data
* @throws Exception if the classifier has not been generated successfully
*/
public void buildClassifier(Instances instances) throws Exception {
// can classifier handle the data?
getCapabilities().testWithFail(instances);
// remove instances with missing class
instances = new Instances(instances);
instances.deleteWithMissingClass();
m_headerInfo = new Instances(instances, 0);
m_numClasses = instances.numClasses();
m_numAttributes = instances.numAttributes();
m_probOfWordGivenClass = new double[m_numClasses][];
/*
initialising the matrix of word counts
NOTE: Laplace estimator introduced in case a word that does not appear for a class in the
training set does so for the test set
*/
for (int c = 0; c < m_numClasses; c++) {
m_probOfWordGivenClass[c] = new double[m_numAttributes];
for (int att = 0; att < m_numAttributes; att++) {
m_probOfWordGivenClass[c][att] = 1;
}
}
// enumerate through the instances
Instance instance;
int classIndex;
double numOccurences;
double[] docsPerClass = new double[m_numClasses];
double[] wordsPerClass = new double[m_numClasses];
java.util.Enumeration enumInsts = instances.enumerateInstances();
while (enumInsts.hasMoreElements()) {
instance = (Instance) enumInsts.nextElement();
classIndex = (int) instance.value(instance.classIndex());
docsPerClass[classIndex] += instance.weight();
for (int a = 0; a < instance.numValues(); a++)
if (instance.index(a) != instance.classIndex()) {
if (!instance.isMissing(a)) {
numOccurences = instance.valueSparse(a) * instance.weight();
if (numOccurences < 0)
throw new Exception("Numeric attribute values must all be greater or equal to zero.");
wordsPerClass[classIndex] += numOccurences;
m_probOfWordGivenClass[classIndex][instance.index(a)] += numOccurences;
}
}
}
/*
normalising probOfWordGivenClass values
and saving each value as the log of each value
*/
for (int c = 0; c < m_numClasses; c++)
for (int v = 0; v < m_numAttributes; v++)
m_probOfWordGivenClass[c][v] =
Math.log(m_probOfWordGivenClass[c][v] / (wordsPerClass[c] + m_numAttributes - 1));
/*
calculating Pr(H)
NOTE: Laplace estimator introduced in case a class does not get mentioned in the set of
training instances
*/
final double numDocs = instances.sumOfWeights() + m_numClasses;
m_probOfClass = new double[m_numClasses];
for (int h = 0; h < m_numClasses; h++)
m_probOfClass[h] = (double) (docsPerClass[h] + 1) / numDocs;
}
