RadialBasisFunction.cpp

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#include "RadialBasisFunction.h"

GRT_BEGIN_NAMESPACE
 
//Register the RadialBasisFunction module with the WeakClassifier base class
RegisterWeakClassifierModule< RadialBasisFunction > RadialBasisFunction::registerModule("RadialBasisFunction");
 
RadialBasisFunction::RadialBasisFunction(UINT numSteps,Float positiveClassificationThreshold,Float minAlphaSearchRange,Float maxAlphaSearchRange){
 this->numSteps = numSteps;
 this->positiveClassificationThreshold = positiveClassificationThreshold;
 this->minAlphaSearchRange = minAlphaSearchRange;
 this->maxAlphaSearchRange = maxAlphaSearchRange;
 trained = false;
 numInputDimensions = 0;
 alpha = 0;
 gamma = 0;
 weakClassifierType = "RadialBasisFunction";
 trainingLog.setProceedingText("[DEBUG RadialBasisFunction]");
 warningLog.setProceedingText("[WARNING RadialBasisFunction]");
 errorLog.setProceedingText("[ERROR RadialBasisFunction]");
}
 
RadialBasisFunction::~RadialBasisFunction(){
 
}

RadialBasisFunction::RadialBasisFunction(const RadialBasisFunction &rhs){
 *this = rhs;
}

RadialBasisFunction& RadialBasisFunction::operator=(const RadialBasisFunction &rhs){
 if( this != &rhs ){
 this->numSteps = rhs.numSteps;
 this->alpha = rhs.alpha;
 this->gamma = rhs.gamma;
 this->positiveClassificationThreshold = rhs.positiveClassificationThreshold;
 this->minAlphaSearchRange = rhs.minAlphaSearchRange;
 this->maxAlphaSearchRange = rhs.maxAlphaSearchRange;
 this->rbfCentre = rhs.rbfCentre;
 this->copyBaseVariables( &rhs );
 }
 return *this;
}

bool RadialBasisFunction::deepCopyFrom(const WeakClassifier *weakClassifer){
 if( weakClassifer == NULL ) return false;
 
 if( this->getWeakClassifierType() == weakClassifer->getWeakClassifierType() ){
 //Call the = operator
 *this = *(RadialBasisFunction*)weakClassifer;
 return true;
 }
 return false;
}

bool RadialBasisFunction::train(ClassificationData &trainingData, VectorFloat &weights){
 
 trained = false;
 numInputDimensions = trainingData.getNumDimensions();
 rbfCentre.clear();
 
 //There should only be two classes in the dataset, the positive class (classLable==1) and the negative class (classLabel==2)
 if( trainingData.getNumClasses() != 2 ){
 errorLog << "train(ClassificationData &trainingData, VectorFloat &weights) - There should only be 2 classes in the training data, but there are : " << trainingData.getNumClasses() << std::endl;
 return false;
 }
 
 //There should be one weight for every training sample
 if( trainingData.getNumSamples() != weights.getSize() ){
 errorLog << "train(ClassificationData &trainingData, VectorFloat &weights) - There number of examples in the training data (" << trainingData.getNumSamples() << ") does not match the lenght of the weights vector (" << weights.size() << ")" << std::endl;
 return false;
 }

 //STEP 1: Estimate the centre of the RBF function as the weighted mean of the positive examples
 const UINT M = trainingData.getNumSamples();
 rbfCentre.resize(numInputDimensions,0);
 
 //Search for the sample(s) with the maximum weight(s)
 Float maxWeight = 0;
 Vector< UINT > bestWeights;
 for(UINT i=0; i<M; i++){
 if( trainingData[i].getClassLabel() == WEAK_CLASSIFIER_POSITIVE_CLASS_LABEL ){
 if( weights[i] > maxWeight ){
 maxWeight = weights[i];
 bestWeights.clear();
 bestWeights.push_back(i);
 }else if( weights[i] == maxWeight ){
 bestWeights.push_back( i );
 }
 }
 }
 
 //Estimate the centre of the RBF function as the weighted mean of the most important sample(s)
 const UINT N = (UINT)bestWeights.size();
 
 if( N == 0 ){
 errorLog << "train(ClassificationData &trainingData, VectorFloat &weights) - There are no positive class weigts!" << std::endl;
 return false;
 }
 
 for(UINT i=0; i<N; i++){
 for(UINT j=0; j<numInputDimensions; j++){
 rbfCentre[j] += trainingData[ bestWeights[i] ][j];
 }
 }
 
 //Normalize the RBF centre by the positiveWeightSum so we get the weighted mean 
 for(UINT j=0; j<numInputDimensions; j++){
 rbfCentre[j] /= Float(N);
 }
 
 //STEP 2: Estimate the best value for alpha
 Float step = (maxAlphaSearchRange-minAlphaSearchRange)/numSteps;
 Float bestAlpha = 0;
 Float minError = grt_numeric_limits< Float >::max();
 
 alpha = minAlphaSearchRange;
 while( alpha <= maxAlphaSearchRange ){
 
 //Update gamma (this is used in the rbf function)
 gamma = -1.0/(2.0*grt_sqr(alpha));
 
 //Compute the weighted error over all the training samples given the current alpha value
 Float error = 0;
 for(UINT i=0; i<M; i++){
 bool positiveSample = trainingData[ i ].getClassLabel() == WEAK_CLASSIFIER_POSITIVE_CLASS_LABEL;
 Float v = rbf(trainingData[ i ].getSample(),rbfCentre);
 
 if( (v >= positiveClassificationThreshold && !positiveSample) || (v<positiveClassificationThreshold && positiveSample) ){
 error += weights[i];
 }
 }
 
 //Check if the current error is the best so far
 if( error < minError ){
 minError = error;
 bestAlpha = alpha;
 
 //If the minimum error is zero then we can stop the search
 if( minError == 0 )
 break;
 }
 
 //Update alpha
 alpha += step;
 }
 
 alpha = bestAlpha;
 gamma = -1.0/(2.0*grt_sqr(alpha));
 trained = true;
 
 std::cout << "BestAlpha: " << bestAlpha << " Error: " << minError << std::endl;
 
 return true;
}

Float RadialBasisFunction::predict(const VectorFloat &x){
 if( rbf(x,rbfCentre) >= positiveClassificationThreshold ) return 1;
 return -1;
}
 
Float RadialBasisFunction::rbf(const VectorFloat &a,const VectorFloat &b){
 const UINT N = (UINT)a.size();
 //Compute the RBF distance, this uses the squared euclidean distance
 Float r = 0;
 for(UINT i=0; i<N; i++){
 r += SQR(a[i]-b[i]);
 }
 return exp( gamma * r );
}
 
bool RadialBasisFunction::saveModelToFile( std::fstream &file ) const{
 
 if(!file.is_open())
 {
 errorLog <<"saveModelToFile(fstream &file) - The file is not open!" << std::endl;
 return false;
 }
 
 //Write the WeakClassifierType data
 file << "WeakClassifierType: " << weakClassifierType << std::endl;
 file << "Trained: "<< trained << std::endl;
 file << "NumInputDimensions: " << numInputDimensions << std::endl;
 
 //Write the RadialBasisFunction data
 file << "NumSteps: " << numSteps << std::endl;
 file << "PositiveClassificationThreshold: " << positiveClassificationThreshold << std::endl;
 file << "Alpha: " << alpha << std::endl;
 file << "MinAlphaSearchRange: " << minAlphaSearchRange << std::endl;
 file << "MaxAlphaSearchRange: " << maxAlphaSearchRange << std::endl;
 file << "RBF: ";
 for(UINT i=0; i<numInputDimensions; i++){
 if( trained ){
 file << rbfCentre[i] << "\t";
 }else file << 0 << "\t";
 }
 file << std::endl;
 
 //We don't need to close the file as the function that called this function should handle that
 return true;
}

bool RadialBasisFunction::loadModelFromFile( std::fstream &file ){
 
 if(!file.is_open())
 {
 errorLog <<"loadModelFromFile(fstream &file) - The file is not open!" << std::endl;
 return false;
 }
 
 std::string word;
 
 file >> word;
 if( word != "WeakClassifierType:" ){
 errorLog <<"loadModelFromFile(fstream &file) - Failed to read WeakClassifierType header!" << std::endl;
 return false;
 }
 file >> word;
 
 if( word != weakClassifierType ){
 errorLog <<"loadModelFromFile(fstream &file) - The weakClassifierType:" << word << " does not match: " << weakClassifierType << std::endl;
 return false;
 }
 
 file >> word;
 if( word != "Trained:" ){
 errorLog <<"loadModelFromFile(fstream &file) - Failed to read Trained header!" << std::endl;
 return false;
 }
 file >> trained;
 
 file >> word;
 if( word != "NumInputDimensions:" ){
 errorLog <<"loadModelFromFile(fstream &file) - Failed to read NumInputDimensions header!" << std::endl;
 return false;
 }
 file >> numInputDimensions;
 
 
 file >> word;
 if( word != "NumSteps:" ){
 errorLog <<"loadModelFromFile(fstream &file) - Failed to read NumSteps header!" << std::endl;
 return false;
 }
 file >> numSteps;
 
 file >> word;
 if( word != "PositiveClassificationThreshold:" ){
 errorLog <<"loadModelFromFile(fstream &file) - Failed to read PositiveClassificationThreshold header!" << std::endl;
 return false;
 }
 file >> positiveClassificationThreshold;
 
 file >> word;
 if( word != "Alpha:" ){
 errorLog <<"loadModelFromFile(fstream &file) - Failed to read Alpha header!" << std::endl;
 return false;
 }
 file >> alpha;
 
 file >> word;
 if( word != "MinAlphaSearchRange:" ){
 errorLog <<"loadModelFromFile(fstream &file) - Failed to read MinAlphaSearchRange header!" << std::endl;
 return false;
 }
 file >> minAlphaSearchRange;
 
 file >> word;
 if( word != "MaxAlphaSearchRange:" ){
 errorLog <<"loadModelFromFile(fstream &file) - Failed to read MaxAlphaSearchRange header!" << std::endl;
 return false;
 }
 file >> maxAlphaSearchRange;
 
 file >> word;
 if( word != "RBF:" ){
 errorLog <<"loadModelFromFile(fstream &file) - Failed to read RBF header!" << std::endl;
 return false;
 }
 rbfCentre.resize(numInputDimensions);
 
 for(UINT i=0; i<numInputDimensions; i++){
 file >> rbfCentre[i];
 }
 
 //Compute gamma using alpha
 gamma = -1.0/(2.0*SQR(alpha));
 
 //We don't need to close the file as the function that called this function should handle that
 return true;
}

void RadialBasisFunction::print() const{
}
 
VectorFloat RadialBasisFunction::getRBFCentre() const{
 return rbfCentre;
}
 
UINT RadialBasisFunction::getNumSteps() const{
 return numSteps;
}

Float RadialBasisFunction::getPositiveClassificationThreshold() const{
 return positiveClassificationThreshold;
}

Float RadialBasisFunction::getAlpha() const{
 return alpha;
}

Float RadialBasisFunction::getMinAlphaSearchRange() const{
 return minAlphaSearchRange;
}

Float RadialBasisFunction::getMaxAlphaSearchRange() const{
 return maxAlphaSearchRange;
}

GRT_END_NAMESPACE