Pie and Bar Charts for Data Analysis
Pie and bar charts, used to display categorical data or data summaries such as proportions, are ubiquitous; everyone knows them. They're simple to produce and understand -- sometimes. Since most survey questions have categorical responses, these charts are liberally used. But they have problems.
Data visualization experts abhor pie charts. Tufte, probably the most dominant and best known data visualization expert, once wrote: “The only thing worse than a pie chart is several of them.” (Tufte, 1983). Pie charts are not effective data displays because we have problems with angles, especially comparing them, just as we have problems with large tables. Lengths are easier for us to see ...