Bar charts
What are they?
Bar charts display data using (you guessed it) bars that are proportional to the values they represent. There are several different types of bar charts depending on the data and the story the chart is telling. Bar chart data is categorical and answers the question “how many” are in each category.
Ribbon charts illustrate change in rankings among categories over time. Each category is represented by a segment within stacked bars. These segments are connected across the bars to form continuous ribbons. The segments are ordered from the largest at the top to the smallest at the bottom, allowing for a clear visual representation of how each category's rank evolves.
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Waterfall charts show how a starting value changes through a series of positive and negative adjustments, leading to a final value. They are useful for breaking down financial data, like showing how different factors add up to a total. Because waterfall charts have a complex visual structure, they can cause confusion for audiences. Consider using bar charts, line charts or stacked bar charts to represent changes over time before using a waterfall chart
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Consider other chart types before using
Consider other chart types before using charts with this label. They might be appropriate, but less familiar charts are often misinterpreted—book office hours with the data viz team if you’re unsure.
Bar Chart Guidelines
X & Y Axis
Include an x-axis on column charts to establish a baseline. For bar charts, include a y-axis. Don’t let the columns or bars float without the clearly defined baseline.
Zero baseline
Columns and bars always should start at a zero baseline. If the columns/bars are similar in height and the differences are important but indistinguishable, consider a line chart, where a zero baseline isn’t required, or use columns/bars but plot the change or percent change.
Data over time
When showing data over time, try use columns instead of bars. Time is easier to read left to right than up and down. If you must plot time this way, start with the most recent data point at the top.
Sort, sort, sort!
Sort the bars (or columns) by greatest to least or least to greatest unless there is a category order you must follow. Don’t put the bars (or columns) in a random order.
Gridlines or direct labels
Use one or the other, you generally don't need both.
Use one color if bars show the same categorical data
If for example, the categories are showing ROI values for 4 quarters, use the same color for the four bars.
Use color to highlight the most important aspect of the story
Use gray to de-emphasize bars that are less important.
