A differential evolution algorithm to optimise the combination of classifier and cluster ensembles

Unsupervised models can provide supplementary soft constraints to help classify new data since similar instances are more likely to share the same class label. In this context, this paper reports on a study on how to make an existing algorithm, named C³E from consensus between classification and clustering ensembles, more convenient by automatically tuning its main parameters. The C³E algorithm is based on a general optimisation framework that takes as input class membership estimates from existing classifiers, and a similarity matrix from a cluster ensemble operating solely on the new target data to be classified, in order to yield a consensus labelling of the new data. To do so, two parameters have to be defined a priori by the user: the relative importance of classifier and cluster ensembles, and the number of iterations of the algorithm. We propose a differential evolution DE algorithm, named dynamic DE D²E, which is a computationally efficient alternative for optimising such parameters. D²E provides better results than DE by dynamically updating its control parameters. Moreover, competitive results were achieved when comparing D²E with three state-of-the-art algorithms.