It is no longer possible to imagine our everyday life without time series data. This includes, for example, market developments, COVID-19 cases, electricity prices, and other data from a wide variety of domains. An important task in the analysis of these data is the detection of anomalies. In most cases, this is accomplished by examining individual time series. In our work, we use the techniques of cluster analysis to establish a relationship between time series and groups of time series. This relationship allows us to observe the development of time series in their entirety, thereby gaining additional insights. Our approach identifies outliers with a real-world reference and enables the user to locate outliers without prior knowledge. To underline the strengths of our approach, we compare our method with another known method on two real-world datasets. We found that our solution needs significantly fewer calculations, produces more reasonable results, and can be applied to real-time data. Moreover, our method detected additional outliers, whose occurrence could be explained by real events.
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