How do you pick the right chart for your data?
If you have data you want to visualize, make sure you use the right charts. While your data might work with multiple chart types, it's up to you to select the one that ensures your message is clear and accurate. Remember, data is only valuable if you know how to visualize it and give context.
What story does your data tell?
Before making a chart, it's important to understand why you need one. Charts, maps, and infographics help people understand complex data, find patterns, identify trends, and tell a story. Think about the message you want to share with your audience.
Follow the best charting practices. Your numbers need to add up, and charts need to be scaled accordingly. What would you like to show? There are four main use cases for charts:
- Comparison
Comparison charts are used to compare one or more datasets. They can compare items or show differences over time. - Relationship
Relationship charts are used to show a connection or correlation between two or more variables. - Composition
Composition charts are used to display parts of a whole and change over time. - Distribution
Distribution charts are used to show how variables are distributed over time, helping identify outliers and trends.
Ask yourself how many variables do you want to show, how many data points you want to display and how you want to scale your axis.
Line, bar, and column charts represent change over time. Pyramids and pie charts display parts-of-a-whole. While scatter plots and treemaps are helpful if you have a lot of data to visualize.
Types of charts
Line charts
A line chart reveals trends or changes over time. Line charts can be used to show relationships within a continuous data set. They can be applied to a wide variety of categories, including the daily number of visitors to a site or variations in stock prices.
- Label your axes clearly. Make sure the viewer knows what they are evaluating.
- Remove distracting chart elements. Grids, varying colors, and bulky legends can distract the viewer from quickly seeing the overall trend.
- Zoom in on the y-axis if your data set starts above zero. In some instances, changing the scale of the y-axis makes it easier for the viewers to comprehend the data.
- Avoid comparing more than 5-7 lines. You don't want your chart to become cluttered or hard to read. Visualize the data you need to tell your story, nothing more.
Pie charts
The pie chart is one of the most used chart types of all time. They are used to display parts of a whole. A pie chart represents numbers in percentages, and the total sum of all the divided segments equalling to 100 percent.
- Make sure your segments add up to 100. Sounds obvious, but this is a common mistake.
- Keep it clean and consistent. Compare just a few categories to get your point across. If the pie slices have roughly the same size, consider using a bar or column chart instead.
- Avoid using 3-D imagery or tilting your pie chart. This often makes your data impossible to read, as the viewer is trying to compare angles quickly.
Bar charts and column charts
Bar and column charts are used to compare different items. Bars on a column chart are vertical, while bars on a bar chart are horizontal. Bar charts are generally used to help avoid clutter when one data label is long or if you have more than ten items to compare. They are easy to understand and to create.
- Start the y-axis at zero. Our eyes are sensitive to the area of bars on a chart. If those bars are truncated, the viewer might draw the wrong conclusions.
- Label the axes. Labeling the axes gives your viewer context.
- Put value labels on bars. This helps preserve the clean lines of the bar lengths.
- Avoid using too many colors. Using a single color or varying shades of the same color is a much better practice. You can highlight one bar in particular if that is the message you want to get across.
Treemaps
Treemaps show parts of a whole. They display hierarchical information as a cluster of rectangles varying in size and color, depending on their data value. The size of each rectangle represents a quantity, while the color can represent a number value or a category.
Treemaps allow you to view trends and make comparisons quickly, especially if one color is particularly prominent. While spreadsheets can show multiple rows of data, treemaps can accommodate hundreds of thousands of items in one organized display, making it easy to spot patterns in seconds. Plus, if made correctly, they make very efficient use of space.
- Start with clean data and a clear message. Treemaps can often involve a lot of data, so it's essential to know what exactly you want to highlight.
- Use bright, contrasting colors, so each region is easily visible. But, remember to avoid the 'rainbow effect'. Choose your colors wisely.
- Label each region appropriately with text or numbers. This makes it easier for the viewer to evaluate your treemap quickly, without error.
- Avoid cluttering your treemap with too many boxes. Treemaps can contain any number of boxes, but space is limited! You don't want your treemap to be hard to read.
Area charts
Area charts are a lot like line charts, with a few subtle differences. They can both show change over time, overall trends, and continuity across a dataset. But, while area charts may function the same way as line charts, the space between the line and axis is filled in, indicating volume.
- Make it easy to read and avoid occlusion. This happens when one or more layers cover important information on the chart.
- Use a stacked area chart. If you have multiple data sets and want to emphasize part-to-whole relationships.
- Use area charts to look at the bigger picture. Take the population, for example. Line charts are useful for showing the net change in population over time, while area charts are good for showing the total population over time.
- Avoid comparing too many datasets. Use a line chart instead, its cleaner.
- Give the proper context with appropriate labels and legends.
Pyramind charts and funnel charts
Pyramid charts (triangle chart or triangle diagram) are a fun way to visualize foundation-based relationships. They appear in the form of a triangle that has been divided into horizontal sections with categories labeled according to their hierarchy. Pyramid charts can be oriented up or down, depending on the relationships they represent. The stacked layers can also show the order of steps in a particular process.
A funnel chart displays values of progressively decreasing proportions. The size of the area is determined by the value as a percentage. This type of chart is often used by sales teams to display stages of sales progress or potential sales in the future. It can also just be a way to show a sales report.
- Pick a topic and create precise subcategories. Decide what information you want to convey with your pyramid/funnel and label your layers clearly.
- Organize your subcategories. Decide on the order and value of each section of your pyramid, and organize them based on their hierarchy.
- Be consistent. Keep the spacing of your sections even and pick an unobtrusive color palette.
- Keep subcategories to a minimum. Adding many layers and colors can make your pyramid hard to read.
Word clouds
Word clouds (also known as tag clouds) are a type of weighted list. Word clouds display text in varying font sizes, weight, or colors to show frequencies or categories. They can be arranged alphabetically or at random. Word clouds help people identify trends and patterns that might be difficult to see otherwise.
- Provide context. Word clouds are visually eye-catching and provide information about frequency, but they often don't give the viewer any context.
- Use word clouds to show frequency. Avoid using them to display complex topics like the budget or healthcare crisis.
- Watch your word length. Longer words take up more space and can be misleading.
- Avoid making your words too similar in size or color.