Lets say I have the following data:
Category positive neutral negative total 0 Category 1 1.000000 0.000000 0.0 2 1 Category 2 1.000000 0.000000 0.0 1 2 Category 3 0.222222 0.277778 0.5 18
The data represents the proportion of each category that are positive/neutral/negative (valence), and I want to communicate 2 pieces of information with a graph:
- Positive + neutral + negative make up 100% of each category
- Whether the category is primarily made up of positive/neutral/negative and their relative proportions
Stacked bar chart
The first thing I tried was a stacked bar chart:
With a stacked bar chart its not clear what values represent. For example, how should Category 3 negative group be interpreted? Is it 50% because it covers only half of the vertical height of the bar? Or is it actually 100%, just that positive and neutral are covering the bottom half?
Also, I think the valence proportions are unclear due to the stacking. For example, what proportion of Category 3 is neutral? Its unclear because the baseline has been elevated and no longer at 0.
Grouped bar chart
Next I tried a grouped bar chart:
I think this solves the baseline problem, and its easy to compare relative proportions within each category, but it introduces 2 new problems:
- Categories where only a single valence is represented (e.g. Categories 1 and 2) only have 1 bar, creating an unbalanced graph. This could potentially confuse the user briefly, until they realize those bars are at 100%
- For Category 3, its no longer clear that positive + neutral + negative make up 100% of the data within that group.
I did also briefly consider a grouped bar chart with raw count values instead of percentages, but this is problematic because totals across categories are quite unbalanced (e.g. 18 vs. 1), and what I'm primarily interested in is valence distribution within each category (i.e. are there more positive than negative in Category 3?)
Whats the most effective way to communicate this type of data? Is this one of the rare occasions where a pie chart is recommended?