Several PhD students (both Aberdeen and non-Aberdeen) have recently shown me paper drafts which included diagrams that were difficult to understand. I thought I would try to write some simple actionable advice on problems with diagrams and what to do about them.

None of the below is rocket science, and many other people have made similar comments. Nevertheless these are problems that I often see in papers I review, as well as in drafts from students,

Text in diagrams: readable and meaningful

The single most common complaint I have about diagrams is that they contain text with miniscule font size. This is not acceptable! The ACL ARR guidelines state that

For any text or numbers in tables and figures, whenever possible, please use the font size of the document text. As a rule of thumb, any text or numbers should be clearly readable when the paper is printed on A4 paper. Submissions that abuse the font size or spacing for figures/tables may be desk rejected.

This rule is widely violated; I remember on one occasion several months ago a student showed me a draft paper which included a figure that needed 400% zoom to be legible. The student did not see anything wrong with this, but it is not acceptable to readers (as well as violating above guidelines), and may lead to papers being rejected (I certainly mark down papers with miniscule fonts when I review them).

Another point is that labels in a diagram need to be meaningful. Eg, “readability score”, not “score1”. If for space reasons you need to use abbreviated label, make them meaningful (eg, “read” as abbreviation for “readability score”), and explain them in the caption.

I suspect this problem arises because many people automatically generate graphs and diagrams from datasets which have generic columns like “score1”. Its fine to use such datasets for research, but they are not acceptable as labels inside diagrams in publications.

Information design: Keep it simple

Information design is very important for diagrams and graphs. Decide on what insights and key information you want to communicate, and design the diagram and graph to meet your communication goal. This is much more important than creating something that looks visually impressive or artistic!

Also, keep it simple! Designing simple digrams or graphs which are effective is usually much easier than designing complex diagrams which are effective. So if you are not an experienced graphic or information designer, you should “keep it simple”. Indeed experienced designers also often go for the simple approach.

This comes up a lot when I comment on draft papers from students. Examples include:

• Two students recently showed me papers which contained complex bar charts which were difficult to interpret. One student had created a grouped bar chart, where the grouping made little sense; indeed in order to understand the impact on the research question, I had to mentally add up the bars in each group. Another student showed me a stacked bar chart where the feature used for the stacked components was not very important; again this just made the chart confusing. In both cases, a simple basic bar chart would have been better for communicating the underlying insights about the research question.

• Another student recently showed me a paper which included very complex diagrams, which would have required at least 5 minutes to understand. I think their goal was laudable, to give the reader lots of information about the system and evaluation. But complexity of the diagrams distracted me from the core content.

• Finally, yet another student showed me a paper which had a complex diagram which could be replaced by a fairly simple table. I recommended doing this, the table was not very impressive visually but was easier for readers to understand.

A common theme in many of the above cases is that the students saw an opportunity to include more information in the diagram, and thought this was a good thing. But too much “secondary” information can distract the reader from the key information and insights. If secondary information is presented, it must be done in a way which does not distract from the key messages.

Again, my advice here is to use simple diagrams which communicate the key messages. Avoid complex visualisations, and dont try to communicate too much information in a diagram.

Make diagrams accessible and culturally neutral

Finally, diagrams should be easily understandable by all readers, including readers with disabilities and from different cultures. There are of course many guides to accessibility for diagrams (eg, from UK government or WCAG Guidelines), but I think the core principles are

• Keep the diagram simple and avoid visual clutter or complexity
• Use san-serif fonts
• Don’t use red/green colours to communicate information
• Provide a text alternative for diagrams

A related issue is not making cultural assumptions. For example, in UK the colour green is often used to show successful outcomes, but in some Asian cultures green is associated with nausea and sickness. Don’t assume that your readers will interpret colours the same way that you do!

Dont get carried away by tools

As a final comment, modern graphing and diagramming tools are very powerful, which means that it is relatively easy to produce very complex and visually appealing diagrams. But such diagrams may not be useful or effective! Focus on creating diagrams which are useful in getting yout insights across to readers, not on using all of the diagramming power available to you.