public static <E extends DataElement> double computeSquareError(CentroidCluster<E> cluster) {
List<E> elements = cluster.getDataElements();
if (elements.isEmpty()) {
return 0;
}
DoubleVector center = cluster.computeCentroid();
double totalError = 0;
final int vectorSize = center.size();
for (DataElement e : elements) {
DoubleVector elemVector = e.asVector();
double errorWithinCluster = 0;
for (int i = 0; i < vectorSize; i++) {
errorWithinCluster += MathUtil.square(elemVector.get(i) - center.get(i));
}
totalError += errorWithinCluster;
}
return totalError;
}