A Group-Based Distance Learning Method for Semisupervised Fuzzy Clustering

Learning a proper distance for clustering from prior knowledge falls into the realm of semisupervised fuzzy clustering. Although most existing learning methods take prior knowledge (e.g., pairwise constraints) into account, they pay little attention to local knowledge of data, which, however, can be utilized to optimize the distance. In this article, we propose a novel distance learning method, which learns from the
Group
-level information, for semisupervised fuzzing clustering. We first present a new format of constraint information, called
Group
-level constraints, by elevating the pairwise constraints (must-links and cannot-links) from
point
level to
Group
level. The
Groups
, generated around data points contained in the pairwise constraints, carry not only the local information of data (the relation between close data points) but also more background information under some given limited prior knowledge. Then, we propose a novel method to learn a distance by using the
Group
-level constraints, namely,
Group
-based distance learning, in order to optimize the performance of fuzzy clustering. The distance learning process aims to pull must-link
Groups
as close as possible while pushing cannot-link
Groups
as far as possible. We formulate the learning process with the weights of constraints by invoking some linear and nonlinear transformations. The linear
Group
-based distance learning method is realized by means of semidefinite programming, and the nonlinear learning method is realized by using the neural network, which can explicitly provide nonlinear mappings. Experimental results based on both synthetic and real-world datasets show that the proposed methods yield much better performance compared to other distance learning methods using pairwise constraints.