/**
* This method can be used to permute the data instances IDs in a collection. This should have a
* similar effect to permuting class labels. It can be used for validation experiments.
*
* @param instances Data instances to be permuted
* @param random Random number generator
* @return Permuted data instances
*/
public static HashMap<String, String> PermuteIDs(HashMap<String, String> map, Random random) {
ArrayList<String> instanceIDs =
ListUtilities.Shuffle(new ArrayList<String>(map.keySet()), random);
ArrayList<String> values = new ArrayList<String>(map.values());
HashMap<String, String> permutedInstances = new HashMap<String, String>();
for (int i = 0; i < instanceIDs.size(); i++)
permutedInstances.put(instanceIDs.get(i), values.get(i));
return permutedInstances;
}
/**
* For a list of String values, this method calculates the frequency at which each unique value
* occurred.
*
* @param values List of values to evaluate
* @return Map between the values and their frequency of occurrence
*/
public static HashMap<String, Integer> GetFrequencyMap(ArrayList<String> values) {
HashMap<String, Integer> map = new HashMap<String, Integer>();
for (String unique : ListUtilities.GetUniqueValues(values)) {
int count = 0;
for (String value : new ArrayList<String>(values))
if (value != null && value.equals(unique)) count++;
map.put(unique, count);
}
return map;
}
public static <T> T[] toArray(Set<T> set) {
return ListUtilities.toArray(toList(set));
}