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Bar Charts |
Bar Chart Definition
A bar chart (also known as a bar graph) is meant to compare set values with proportionally sized rectangles. It is often thought of as the easiest data visualization to understand and use, which might be the contributing factor to its enormous popularity worldwide.
There are a number of ways you can present data within a bar chart: horizontally, vertically, segmented, grouped, stacked, and more. Its most common use is to visualize the relative measures, frequency, performance, etc. of many data groups at once—for instance, in the bar chart example below we can see the comparative duration of the employee hiring process for 25 different countries.
As you can see from this vertical bar chart (also known as a column chart), one axis shows the comparative variable (in this case, “Country,” plotted on the x-axis) and another axis depicts a numerical scale (in this case, “Number of Days”). The labels act as visual aids to help with reading the actual figures represented by each bar.
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Longer descriptions are harder to fit into the bar width when you are comparing a larger number of categories. There are two ways that this problem can be approached; the first is to use acronyms, abbreviations or to shorten the terms (for example, above we used three-letter abbreviations for the name of each country. The second approach is to flip the chart on its tail—literally! A horizontal bar chart gives far more room for descriptive terms.
Using a shorter, abbreviated format for the dates in the example above would make the chart much more difficult to read when the width of the bars is considered. The horizontal plotting makes the information presented far more accessible, which is always the aim of any data visualization.
Tip! Create a horizontal bar chart in seconds with Vizzlo—it has its very own Vizzard!
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What Are the Different Kinds of Bar Charts?
Double/Grouped Bar Chart
Double bar charts and grouped bar charts add two or more subgroups to the main categories, respectively. They can also be referred to as clustered bar graphs, multi-set bar charts, or grouped column charts. They are useful to compare, for example, sales of different products or channels from one year to the next. Or, like in the grouped bar example below, the survey information is broken down further into the researched countries:
When creating a double or grouped bar chart, it is essential to color code the different variables and provide a key explanation for the viewer’s reference.
Create your grouped bar chart here with our dedicated Vizzard.
Stacked Bar Chart
Stacked bar charts add an additional function to regular ole’ bar charts—of course, they still compare different categories, but also illustrate the contributing factors to the final value. That is, use a stacked bar chart when the sum of the amounts represented by the individual stacked bars adds additional information to the chart.
In the example below, we can see the overall earnings of a selection of Pixar movies, but also the proportion of that figure that was spent on making each film.
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Segmented Bar Chart
Segmented bar charts (also known as “100% stacked bar charts”) always show each bar with the same, unified length and a complete value of 100%. The focus here is on the breakdown of each comparative category and their relative sizes rather than their absolute, cumulative values.
In this 100% stacked bar chart, we don’t need to know how many managers or vice-presidents there are in total; to show the comparatively smaller number of C-suite officers than entry-level professionals may give a skewed perspective on the respective importance or power held by these positions. The proportion of those roles that are held by either men or women is the point of interest here.
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Technically, there is a difference between a bar graph and a histogram: a bar graph compares different discrete categories, whereas a histogram groups a continuous variable into bins with and counts the observations in each bin.
Below is and example that shows the age distribution among the Titanic passengers.
Although a bar chart and a histogram share an almost identical appearance they should not be confused with each other. A histogram shows the distribution of a continuous variable while a bar chart displays a quantitative value for a set of categories.
Development and History of the Bar Chart
Unusually for such a simple and universally popular diagram, the bar chart did not develop organically over time, with many vague and mysterious sources, but was conceived by a single man (William Playfair) in 1781.
William Playfair, the Scottish engineer, political economist, and scoundrel, was inspired by Joseph Priestley’s creation of the timeline chart in 1765 as a way of visualizing and comparing information. The major difference between previous data visualizations and Playfair’s invention was that his bar charts measured data by a set (any set) of comparative values, whereas all that had come before was measured either by time (as with Priestly’s timelines) or space (such as coordinates). Just as every data viz evangelist now would agree, Playfair believed that visuals such as charts communicated information much more clearly than tables of raw data.
Fun fact! William Playfair held over 20 professions during his lifetime - including working for the British Government as a secret agent in France.
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To summarize, a bar chart is:
Vizzlo's bar charts: examples and key features
- Vertical and horizontal views
- Growth rates (CAGR), reference lines, trendlines, and benchmarks
- Custom number formats and colors