public Classification classify(Instance instance) {
FeatureVector fv = (FeatureVector) instance.getData();
assert (instancePipe == null || fv.getAlphabet() == this.instancePipe.getDataAlphabet());
Node leaf = getLeaf(m_root, fv);
return new Classification(instance, this, leaf.getGainRatio().getBaseLabelDistribution());
}
public void addToken(FeatureVector fv) {
int[] indices = fv.getIndices();
Alphabet dictionary = fv.getAlphabet();
int indicesLength = fv.numLocations();
for (int i = 0; i < indicesLength; i++) {
String key = dictionary.lookupObject(indices[i]).toString();
// log.info( key );
if (!contextOnly
|| (contextOnly
&& (key.endsWith("/+1")
|| key.endsWith("/-1")
|| key.endsWith("/-2")
|| key.endsWith("/+2")))) {
map.increment(key);
}
}
}
/**
* Classify an instance using NaiveBayes according to the trained data. The alphabet of the
* featureVector of the instance must match the alphabe of the pipe used to train the classifier.
*
* @param instance to be classified. Data field must be a FeatureVector
* @return Classification containing the labeling of the instance
*/
public Classification classify(Instance instance) {
// Note that the current size of the label alphabet can be larger
// than it was at the time of training. We are careful here
// to correctly handle those labels here. For example,
// we assume the log prior probability of those classes is
// minus infinity.
int numClasses = getLabelAlphabet().size();
double[] scores = new double[numClasses];
FeatureVector fv = (FeatureVector) instance.getData();
// Make sure the feature vector's feature dictionary matches
// what we are expecting from our data pipe (and thus our notion
// of feature probabilities.
assert (instancePipe == null || fv.getAlphabet() == instancePipe.getDataAlphabet());
int fvisize = fv.numLocations();
prior.addLogProbabilities(scores);
// Set the scores according to the feature weights and per-class probabilities
for (int fvi = 0; fvi < fvisize; fvi++) {
int fi = fv.indexAtLocation(fvi);
for (int ci = 0; ci < numClasses; ci++) {
// guard against dataAlphabet or target alphabet growing; can happen if classifying
// a never before seen feature. Ignore these.
if (ci >= p.length || fi >= p[ci].size()) continue;
scores[ci] += fv.valueAtLocation(fvi) * p[ci].logProbability(fi);
}
}
// Get the scores in the range near zero, where exp() is more accurate
double maxScore = Double.NEGATIVE_INFINITY;
for (int ci = 0; ci < numClasses; ci++) if (scores[ci] > maxScore) maxScore = scores[ci];
for (int ci = 0; ci < numClasses; ci++) scores[ci] -= maxScore;
// Exponentiate and normalize
double sum = 0;
for (int ci = 0; ci < numClasses; ci++) sum += (scores[ci] = Math.exp(scores[ci]));
for (int ci = 0; ci < numClasses; ci++) scores[ci] /= sum;
// Create and return a Classification object
return new Classification(instance, this, new LabelVector(getLabelAlphabet(), scores));
}
