How To Make Data Viz Accessible

Data visualization is the translation of data in the form of words and numbers to a visual format, using color, size, shape, and placement to convey trends and patterns in the data which can be much less apparent when looking at tables of numbers or words. Thus data viz communicates best to those with full visual capabilities. To make charts, graphs, and maps accessible to those with visual impairment, we must translate the meaning of a visualization back into words, which can be a challenge. Amy Cesal's article, Writing Alt Text for Data Visualization, can help us address that challenge.

Alt text is a brief description meant to provide the meaning and context of a visual item in a digital setting. And although Cesal notes that, in most cases, it’s impossible to write something short that conveys the whole meaning of a visualization, she maintains that an incomplete description is better than none at all. Here are Cesal’s simple guidelines for alt text for data viz:

Chart type: It’s helpful for people with partial sight to know the chart type. This information provides context for understanding the rest of the visual. Example: Line graph.

Type of data: What data is included in the chart? The x and y axis labels may help you figure this out. Example: number of clients served per day in the last year.

Reason for including the chart: Think about why you’re including this visual. What does it show that’s meaningful? There should be a point to every visual and you should tell people what to look for. Example: more clients are served during the winter months.

Cesal also suggests that you include a link to the raw data somewhere in the surrounding text.

For a deeper dive into this topic, checkout Image Description Guidelines from the Diagram Center.

To see past data tips, click HERE.

Let’s talk about YOUR data!

Got the feeling that you and your colleagues would use your data more effectively if you could see it better? Data Viz for Nonprofits (DVN) can help you get the ball rolling with an interactive data dashboard and beautiful charts, maps, and graphs for your next presentation, report, proposal, or webpage. Through a short-term consultation, we can help you to clarify the questions you want to answer and goals you want to track. DVN then visualizes your data to address those questions and track those goals.

What's The Right Text Size to Make Data Viz Accessible?

Here’s another in a series of tips on how to make data visualizations accessible to audience members with issues that affect their ability to see or interact with a visualization. This week it’s text size.

The rule of thumb is: Text must not be smaller than 9 point in size. Ideally only minor text is rendered at 9 point (e.g. axis labels) while all other text is larger. The viz below has a lot of text, and most of it is 9 point. To increase its accessibility, I might increase the key sentences in the captions to 11 point. But, at the least, I’d bump up the 8 point text, near the bottom, to 9 point, which is what you see in the “After” version below.

If you are interested in a deep dive into accessibility issues and solutions, you can find plenty of information online including Chartability.

To see past data tips, click HERE.

Let’s talk about YOUR data!

Got the feeling that you and your colleagues would use your data more effectively if you could see it better? Data Viz for Nonprofits (DVN) can help you get the ball rolling with an interactive data dashboard and beautiful charts, maps, and graphs for your next presentation, report, proposal, or webpage. Through a short-term consultation, we can help you to clarify the questions you want to answer and goals you want to track. DVN then visualizes your data to address those questions and track those goals.

How To Make Your Data Viz More Accessible, Tip#1

If you are trying to reach a large audience with your charts, maps, and graphs, then consider accessibility issues. Even if your data viz is meant for a small, specific audience, you may not be aware that certain people in the group are, for example, color blind or have other issues that affect their ability to see or interact with a visualization.

If you are interested in a deep dive into accessibility issues and solutions, you can find plenty of information online including Chartability. In a series of 60-second data tips, I’m taking on one basic accessibility issue at at time. This week it’s contrast.

Data visualizations must be perceivable to be accessible. This means that users can readily identify content using their senses: sight, sound, and touch. When the contrast between the critical content and the background or adjacent colors is low, the content can be difficult to perceive for some people. So shapes and large text should have more than a 3:1 contrast against background or adjacent content, and regular text should have more than a 4.5:1 contrast. Here’s a tool to determine contrast ratio.

The colors in the first stacked bar chart below have low contrast to each other (less than 2 to 1) and so some may have difficulty distinguishing among the bar segments. The second stacked bar chart, by contrast (pun intended), has a higher ratio (3 to 1) and thus is much easier to perceive.

To see past data tips, click HERE.

Let’s talk about YOUR data!

Got the feeling that you and your colleagues would use your data more effectively if you could see it better? Data Viz for Nonprofits (DVN) can help you get the ball rolling with an interactive data dashboard and beautiful charts, maps, and graphs for your next presentation, report, proposal, or webpage. Through a short-term consultation, we can help you to clarify the questions you want to answer and goals you want to track. DVN then visualizes your data to address those questions and track those goals.