Text clustering with styles

This thesis mainly describes the author clustering problem where, based on a set of n texts, the goal is to determine the number k of distinct authors and regroup the texts into k classes according to their author. We iteratively build a stable and simple model for text clustering with styles. We start by designing a measure reflecting the (un)certainty of the proposed decision such that every decision comes along with a confidence of correctness instead of only giving a single answer. Afterwards, we link those pairs of texts where we see an indication of a shared authorship and have enough evidence that the same person has written them. Finally, after checking every text tuple, if we can link them together, we build the final clusters based on a strategy using a distance of probability distributions. Employing a dynamic threshold, we can choose the smallest relative distance values to detect a common origin of the texts. While in our study we mostly focus on the creation of simple methods, investigating more complex schemes leads to interesting findings. We evaluate distributed language representations and compare them to several state-of-the-art methods for authorship attribution. This comparison allows us to demonstrate that not every approach excels in every situation and that the deep learning methods might be sensitive to parameter settings. The most similar observations (or the category with the smallest distance) to the sample in question usually determines the proposed answers. We test multiple inter-textual distance functions in theoretical and empirical tests and show that the Tanimoto and Matusita distances respect all theoretical properties. Both of them perform well in empirical tests, but the Canberra and Clark measures are even better suited even though they do not fulfill all the requirements. Overall, we can note that the popular Cosine function neither satisfies all the conditions nor works notably well. Furthermore, we see that reducing the text representation not only decreases the runtime but can also increase the performance by ignoring spurious features. Our model can choose the characteristics that are the most relevant to the text in question and can analyze the author adequately. We apply our systems in various natural languages belonging to a variety of language families and in multiple text genres. With the flexible feature selection, our systems achieve reliable results in any of the tested settings.