About Data Visualizations: Bar Graphs
What is a bar graph?
Simple but powerful, bar graphs are one of the most common charts used to compare categorical data, which are data that can be grouped into categories like race and sex.. Bar graphs are also unique in design because they can be displayed horizontally or vertically. Bar graphs are helpful for comparing changes that happen over time, such as years, or comparing differences by category.
Centers for Disease Control and Prevention (Department of Health and Human Services). (2019). CDC Multiple Cause of Death: African american drug overdose death rate (county) [dataset]. Washington, DC: SAGE Stats by SAGE Publishing. Available from http://data.sagepub.com/sagestats/16347.
The above graph tracks the death rate of African Americans per 100,000 persons in Washington, D.C. due to drug overdose. The increasing length of the vertical bars clearly shows a rise in deaths between 2014 and 2017. In this way, bar graphs make it easy to process data and ask questions about it. For instance, this graph guides the reader to question why drug overdose deaths have steadily increased since 2014. This is something the bar graph can’t tell us, but we wouldn’t have come to this question without the bar graph revealing that trend to us.
Tips on creating a bar graph
Excel makes it easy to create a bar graph from scratch with their bar graph feature. However, the guidelines below will make it easy to create a bar graph no matter your platform!
- Have data prepared for your X and Y axis. If you’re using continuous data, which are data values within a certain range, it is visually better to put them on the X axis.
- Add labels and scales for each axis.
- Add rectangular bars to represent your data on the graph.
- Title your graph and make sure it quickly and concisely explains the bar graph.
- Include a legend if necessary.