May 19th, 2021
We want to enable you to better communicate your data — and for us, “better” also means “more nuanced”. Using a confidence interval to show how certain you are (or your data source is) about averages, or adding target markers, are great ways to do just that. You can add both to Datawrapper bar charts with the new option “overlays.”
You will find the option to add an overlay at the bottom of the Refine tab in step 3: Visualize when creating a bar chart. Click on Add overlay and choose one of your uploaded columns for a value ( = line) overlay, or two columns for a range overlay:
Once you create a range overlay, you can change its color and pattern and decide how it should be named in your color key. Value overlays can also be labeled directly over the first bar.
Use our value and range overlays to add confidence intervals, or to compare current values to targets or past plans:
Create as many value and range overlays as you need – you can even stack several of them on top of each other.
You want to try out our new feature? Great! Here are a few recommendations:
Avoid "within-the-bar bias": In a 2014 study, Michael Correll and Michael Gleicher (PDF) found that people judge values inside the bar to be more likely than values outside the bar (when a classical error bar is used). After adding an overlay, ask yourself: Which values would you judge as more likely when seeing this visualization? Can you change the opacity, color, or pattern of the overlay to work against within-the-bar bias?
You could also make the bar completely transparent (e.g. with the hex code
#ffffff00) to just show the ranges. This way, they look similarly important on both sides:
Label your overlays. Range overlays can mean all sorts of things — 95% confidence intervals, 80% confidence intervals, complete range, standard deviation, etc. — and your readers don't know which one you're using. So keep the color key (it's turned on by default), and add an explanation in the description.
Check your labels in the first row on mobile screens. Below each Datawrapper chart, you can check how it'll appear to readers on mobile screens. Use that option to make sure your direct labels don't overlap if you chose Label on first row for your value overlays.
If you want to show more complexity and nuance in your Datawrapper visualizations, confidence intervals might be just the right option. To learn about other possibilities, visit our Academy article Examples of Datawrapper charts that show complex data for box-and-whisker-plot-like charts or combinations of column and line charts. And as always, we love to hear from you. Get in touch at firstname.lastname@example.org with any comments, ideas, or feedback.