A single column bar chart can effectively visualize a sorted and labeled list of numeric records, such as salaries per employee. However, its height limits the number of visible records. As the number of records increase, scrolling requires interaction to see an overview, and using shorter bars hinders observing individual records. For dense visualization of sorted numeric data, we consider two multi-column bar chart designs, wrapped bars and piled bars, in addition to treemaps, a space-filling design that is commonly used to scale in the number of records. We evaluate their design characteristics and graphical perception performance by crowdsourcing under comparison, ranking and overview tasks. Our results suggest that multi-column designs can outperform the space-filling treemap design to show more records for comparison and overview tasks with training.
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