What is Average probabilities? inside the "vote"section - weka

Question

What is the average of probabilities used in Weka? what is the code inside distributionForInstanceAverage doing?

Answer 1

It's just returning the mean of the probability distributions for each of the base classifiers (learnt within Vote or built outside and loaded by Vote).
It first sums them up for any models learnt within Vote, then any loaded in, and then elementwise divides the array by the total number of models.
protected double[] distributionForInstanceAverage(Instance instance) throws Exception {
//Init probs array with first classifier used within model (learnt or loaded)
double[] probs = (m_Classifiers.length > 0)
? getClassifier(0).distributionForInstance(instance)
: m_preBuiltClassifiers.get(0).distributionForInstance(instance);
//Add the distributions of any classifiers built within the Vote classifier to probs array
for (int i = 1; i < m_Classifiers.length; i++) {
double[] dist = getClassifier(i).distributionForInstance(instance);
for (int j = 0; j < dist.length; j++) {
probs[j] += dist[j];
}
}
//Add the distributions of any classifiers built outside of the Vote classifier (loaded in) to the probs array
int index = (m_Classifiers.length > 0) ? 0 : 1;
for (int i = index; i < m_preBuiltClassifiers.size(); i++) {
double[] dist = m_preBuiltClassifiers.get(i).distributionForInstance(instance);
for (int j = 0; j < dist.length; j++) {
probs[j] += dist[j];
}
}
//Divide each probability by the total number of classifiers used in Vote (to get the mean)
for (int j = 0; j < probs.length; j++) {
probs[j] /= (double)(m_Classifiers.length + m_preBuiltClassifiers.size());
}
return probs;
}