The Sawtooh Chart for Compact Cumulative Data Visualization
We introduce the sawtooth chart, a compact representation of cumulative data that splits a continuous line chart into segments once a given value has been reached. All segments are then aligned over an horizontal layout and their slope indicates the time to reach the given value. So vertical segments show a rapid increase while horizontal ones a moderate one. This design was motivated by the COVID-19 deaths to convey how much time it took for countries to reach 500 deaths. The main benefit of the sawtooth chart is that it provides a compact graphics and the slope encoding as segments provide an easier way to compare trends. We report on the technical details and feedback we collected during the design process of this technique which is applicable beyond COVID-19 data and available as an open-source project.