Bar Chart
A bar chart is a graph with rectangular bars. Each bar’s length or height is proportional to the bars’ represented values. In other words, the length or height of the bar is equal to the quantity within that category of data. The graph usually shows a comparison between different categories. Although the graphs can technically be plotted vertically or horizontally, the most usual presentation for a bar graph is vertical, as the picture below shows. The x-axis represents the categories, while the y-axis represents a discrete value for those categories. In the graph below, the discrete values are percentages. |
| bar chart |
A bar graph is useful for looking at a set of data and being able to make visual comparisons. For example, it’s easier to see which items are taking the largest chunk of your budget by glancing at the above chart rather than looking at a set of numbers.
Bar charts can also represent more complex categories with stacked bar charts or grouped bar charts. For example, if you had two houses and needed budgets for each, you could plot them on the same x-axis with a grouped bar chart, using different colors to represent each house.
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| grouped bar chart |
A stacked bar chart is good for showing the total within each individual category, although it makes it hard to tell the difference between the totals in each group.
Stacked bar chart showing list price change announcements by company.
Difference Between a Histogram and a Bar Chart
A bar chart is used for when you have categories of data, like types of movies, music genres, geographical areas or dog breeds. It’s also a good choice when you want to compare things between different groups. You can theoretically use a bar graph if you want to track change over time as long as the changes are significant (for example, decades or centuries). When you have continuous data, like people’s weights or IQ scores, a histogram is best.
