Enhancing Chart Contrast #TweakThursday 43

Comparison is an important objective of data visualization, by which we derive insights in a cohort.

Trellis chart is an interesting way to visualize a large cohort of data. But sometimes we may get lost in the repetition of the same chart type. That is it may not be easy to make some of the cohort standing out. Th choice of chart types can impact the contrast between the members of the cohort.

Here the contrast is not at the pixel level of luminosity, but at the chart level.

Below we will use an example by Josh Preston

https://twitter.com/joshpresto/status/1217522236321603587

As part of the MakeoverMonday project, this is the initial chart that Josh shared on twitter:

The line chart shows well the trend of each sport but it is difficult to view the difference in terms of popularity. In other words, the contrast is low between the members of the cohort.

I suggested him to try an area chart version. Here is what he got:

The amount of ink in the area chart is a big visual differentiator between different sports. This created a large contrast between sports. Here we can think each box in the trellis as a pixel. It's visually striking to the viewers regarding the more popular sports, even if we look at the charts from afar.

Last but not the least, the arrows indicate upward or downward trending. I suggest that we should contrast them as well. It's hard to discern the direction of the arrows because they are small. Josh came up with light/dark grays to differentiate the two trends. This design is especially friendly to the people with color vision deficiency.

In this chart, through contrast, we enhanced the contrast in both the popularity and the trending directions.

(Refresh the page if you want to view the gif image multiple times. Or go to Tableau Public and click the button at the top-right corner.)

Jake and I collaborated on a dashboard. He told me that he learnt a way to create an in-place help page in Tableau. He first saw it at a conference somewhere and couldn't recall who the speaker was. So I am blogging here about it but the credit goes to somebody else. If anyone knows who the original creator is, leave a comment below.

The key idea is to float a semi transparent worksheet on top of the dashboard, where a help text box is strategically placed on top of each chart. This way, we can explain how to view each chart and what data points are important, etc. This worksheet is collapsible by a show/hide button.

Below I would like to show how this worksheet can be constructed.

1. Sheet with a single data mark.

Double click the empty space in Marks panel and add two single quotes. Make the null pill a text label. This creates a single null mark.
Set the view as "Entire View"

2. Create an show/hide button

Go to the target dashboard
Drag a floating vertical container to the dashboard, making it cover all the area of interest.
Drag the Single Null Mark sheet and drop it into the above container. Hide the sheet title.
Create an open/close button for the container and place the button at the top-right corner.

3. Add annotations

Format the sheet background opacity as 70% in the layout manager
Select area annotations and place them anywhere of interest.
Write help text and format it to highlight important messages.
The text can serve as functional guide and/or insight guide.

Here is an example. Feel free to download the workbook and explore. Click the "i" button at the top-right corner to view the in-place help.

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Vizible Difference

In search of data visualization excellence

1. Sheet with a single data mark.

2. Create an show/hide button

3. Add annotations

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