Immunology as a Metaphor for Computational ... - Napier University

Chapter 4. Applying an Immune System Analogy to Data-Clustering Problems 1114.2.2 Non-Stationary DataSection 4.2.1 describes how N antigens can be generated from s schema in equal proportions.All experiments using static data are generated from one of the three categoriesof data described; half-length schema, quarter-length schema and eighth-lengthschema. Each of these three categories contains non-overlapping schema. A more generalmethod of generating data is to also generate the schema randomly, by choosing arandom start point along the string and then setting d contiguous bits to 1. All remainingL d¥ bit positions contain wild-cards. Schemas are more likely to overlap in thiscase, but this is likely to be a more accurate reflection of real data sets. This method£can easily be adapted to produce non-stationary data sets using the algorithm shown infigure 4.1. Generating datasets in this manner enables the proposed algorithms to beevaluated in the context of the following properties of the datasets:1. The number of clusters present in the dataset2. The length of the defined section of each cluster3. The extent of overlap of the clusters4. The rate of change of the dataset in terms of the number of clusters replaced ateach update, and the rate at which the update occurs.This will enable some conclusions to be drawn about the suitability of the suggestedapproaches for clustering real-world datasets, in which sensible estimates can be madeof the likely rate of change of the data, and also of the characteristics of the dataset.4.2.2.1 Relevance of Data Generation Approach to Real DatasetsIn a real dataset, we would expect to observe clusters of data, in which items withineach cluster share common features. However, it is extremely likely that at least someof these clusters will not be distinct but will overlap with each other. Therefore, whendesigning an artificial dataset in order to test the proposed models it is essential thatthe datasets should exhibit at least two characteristics if performance on them is to beindicative of real-world problems: