Use of a Silent Legend

[Jennell_McIntire]

In this blog post, I will revisit a topic that I blogged about over a decade ago, the use of a silent legend. By default, a legend is created in a visualization when there are multiple dimensions and/or measures. The legend helps the user understand the visualization. Legends are helpful and without them, users may not comprehend the data in a visualization. But what do you do if have many visualizations on a sheet? Do you need a legend for each chart? Let’s look at the various ways a legend can be used and how a silent legend can reduce the clutter and give a sheet a cleaner look.

In the screen shot below, there are four visualizations at the bottom of the sheet with legends.

In this app, the legends are all the same because the visualizations are using the same asset class dimension. In this example, the legend does not need to be displayed for each visualization because it is redundant. Let’s see how this sheet will look if only one of the legends are kept on the sheet. A legend can easily be removed by toggling off Show Legend in the properties of the chart.

 Here is what the sheet looks like with just one legend.

The sheet looks better with one legend versus four legends. This use of one legend for four charts, has decluttered the sheet and reduced repetitiveness. If a developer wants a legend to be displayed without expanding the chart, they need to ensure the visualization is large enough. Without the legends in the three stacked bar charts, less space is needed for the charts, thus they can be made smaller, if desired, to take up less space on the sheet. Since all the visualizations at the bottom of the sheet are using the same legend, the legend was placed with the first visualization, assuming a user is reading top to bottom, left to right.

Now, the beauty of a silent legend is that all visualization legends can be removed from a sheet. In the screenshot below, the four headings at the top of the sheet are colored based on the asset class they represent. So, Equity is green, Fixed Income is dark blue and so on.

This is an example of silent legend. The legend is implied by the asset class headings. This option looks even better and cleaner than the sheet with one legend.

The use of a silent legend is possible in this app because there are only four values for asset class. I have seen this work nicely with up to six values. Anything more may become too cumbersome and may require a legend to be used. Also, if the four visualizations at the bottom of the sheet used different dimensions, then multiple legends should be used. Legends are important and they should not be removed to add space if the chart is unreadable without it. What good is a pretty chart if you do not understand it.

Thanks,
Jennell

[Or]

@Jennell_McIntire I'd like to point out that to use this, you'll often want to set the dimension member colors in the master item or otherwise encode them in a fixed manner. If you don't, the colors may change when users make a selection or if a single member happens to be entirely missing from one of the charts, but not others, which is going to be pretty confusing for the user...

Interesting tip on using the headers for legend colors. I wonder, does UX research support this method? It's a great way to save space if you can trust people to notice it.

[barnabyd]

Thanks @Jennell_McIntire, we did something similar recently for one of our clients. A 'silent legend' was used to label two sets of filters with alternate states and then colour code the columns of the table that are based on those filters.

One thing that I think worked well for us is to colour the headings with white text on a coloured background. I feel that the connection between the legend and the data was more obvious than coloured text on white.

Cheers, Barnaby.

[MatheusC]

@Jennell_McIntire  Thank you for the post, the combination of the colors of these legends between graphs that refer to the same dimensions is also important to convey understanding to the end user.
Like a pie chart, and lines or lines and table...

Maintaining the colors, as highlighted by the @Or 

- Matheus

[gomeri]

This method is very intersting. I think that it can be used in a extreme context, but for fluidity and reability of information it can be converted in inverse way. It is possibile to create a generic legend of a group of chart and user it in chart of same group. In this case is important to know Gestalt's principles.

[Jennell_McIntire]

Hi @barnabyd - I would love to see screenshots of what you did if you are able to share. 

[Jennell_McIntire]

@Or Very good point - thank you!

[mshann01]

I would take the declutter even further and remove the x-axis titles from the bar charts.  The title of the chart tells you it is reporting assets.  I often remove gridlines and the x-axis labels as well if I add values to the data points.  I will look to incorporate these additional ideas as well to help in my design.