Visualizing symmetric square matrices with rainbow boxes: methods and application to character co-occurrence matrices in literary texts

A symmetric square matrix is a type of dataset frequently found in various domains. An example is character co-occurrence matrices in digital humanities. However, the visualization of these matrices is difficult. In this paper, we propose a method for visualizing symmetric square matrices, by transforming a matrix into overlapping sets, and then by visualizing these overlapping sets using rainbow boxes, a recent set visualization technique. We apply this method to the visualization of character matrices in novels, using two datasets: a small one (21 characters) and a large one (80 characters). We show that this visualization allows the finding of several insights. Finally, we discuss the advantages and drawbacks of this method, and we compare it to other approaches in the literature.