Then we use the equation c = argmin c i ∈C ||c i − e|| to assign the concept vector e with category c. Since purity works as a standard evaluation metric for clustering (Rothenhäusler and Schütze, 2009), to compare our model with the concept clustering, we also use purity to measure our model's performance.
purity is defined as: where Ω denotes a clustering solution, G is a set of gold standard classes, n is the number of instances, k is the cluster index and j is the class index, ω k represents the set of labels in a cluster and g j is the set of labels in a class.