Cave Plots: A Graphical Technique for Comparing Time Series

Abstract

Cave plots are a good way to compare data from two or more time series, even if the two series are observed at irregular times. Cave plots can show thousands of measurements, but they are readily understood, preserve individual values, highlight short-term, long-term, and periodic fluctuations, and make correlation (or lack of correlation) between two time series apparent. We have used a page of cave plots to show millions of measurements on network reliability and tens of thousands of measurements on air quality. The plots highlight features of the data that warrant a closer look.