public svm_problem do_sample(svm_problem svmProblem) {
logger.debug("Creating " + sample + " sample");
Map<Double, List<Integer>> label2index = new HashMap<Double, List<Integer>>();
for (int i = 0; i < svmProblem.l; ++i) {
double label = svmProblem.y[i];
if (label2index.containsKey(label)) {
label2index.get(label).add(i);
} else {
List<Integer> indeces = new LinkedList<Integer>();
indeces.add(i);
label2index.put(label, indeces);
}
}
for (List<Integer> indeces : label2index.values()) {
Collections.shuffle(indeces);
}
int newSize = (int) (svmProblem.l * sample);
logger.debug("Original size: " + svmProblem.l);
logger.debug("Sample size: " + newSize);
double[] newlabels = new double[newSize];
svm_node[][] newdata = new svm_node[newSize][];
int i = 0;
for (List<Integer> indeces : label2index.values()) {
int catSize = (int) (indeces.size() * sample);
for (int j = 0; j < catSize; ++j) {
int index = indeces.remove(0);
newlabels[i] = svmProblem.y[index];
newdata[i] = svmProblem.x[index];
if (++i >= newSize) {
break;
}
}
if (i >= newSize) {
break;
}
}
// fill any remaining empty items caused due to rounding
if (i < newSize) {
for (List<Integer> indeces : label2index.values()) {
if (indeces.isEmpty()) {
continue;
}
int index = indeces.remove(0);
newlabels[i] = svmProblem.y[index];
newdata[i] = svmProblem.x[index];
if (++i >= newSize) {
break;
}
}
}
svm_problem newProblem = new svm_problem();
newProblem.l = newSize;
newProblem.x = newdata;
newProblem.y = newlabels;
return newProblem;
}
