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Communicating with charts and graphs

By African American Photographs Assembled for 1900 Paris Exposition – Library of Congress

A chart offers the reader an interpretation of the data in a way that should be correct, clear and pleasant. Correctness is of course the most important thing, but aesthetic clarity and pleasantness are closely connected in presenting data correctly and effectively.

Graphs communicate first with shapes and colours. Relevant information passes through visual aspects, by using codes that are widely implicit and used unknowingly.

In fact, we choose to represent the data in a graphic form for its visual impact and capacity to synthesize the information, compared to a table or a written text. And this is the precise reason why, if the graphic is badly designed, the message will be misleading.

‘You see, but you do not observe.’ (A. Conan Doyle)

In particular, if we address an audience of non-specialists, we have to assume that the “normal” reader will not pay particular attention to the texts (except for the captions) (Swires-Hennessy 2014) and will interpret even the scale of the representation on the basis of his knowledge and conventions, for example by ignoring the annotations of the axes.

The cartesian coordinate system is more familiar and intuitive than the polar one (used in pie charts) and the same colours have their own signification system: the scale of intensity, for example, is intuitively associated with that of the values, so that light colours mean “less” and dark ones “more”.

When we perceive differences the world ‘takes form’ in front of us and for us (A. J. Greimas)

Another point to consider is that, in a sign system, meanings are constituted by differences. In a bar chart, for example, the reader will have to notice only the different lengths of the bars, without being “distracted” or “mislead” by other signs, like colours.

Monotony is “boring” and what breaks it, awakens the attention: a change in colours or style activates the reader’s interest, but it could be distracting from the focus of the message and make it more difficult to interpret – unless it is actually significant, and therefore necessary.

Less is more (L. Mies van der Rohe)

This is the reason why the most recent trends in this field go towards the radical simplification, according to the principle of “less is more“: few significant elements, to communicate in a clear and unambiguous way what really matters.


Chen, C., Hardle, W., & Unwin, A. (A c. di). (2007). Handbook of Data Visualization. Berlin: Springer Verlag.

Knaflic, C. N. (2015). Storytelling With Data: A Data Visualization Guide for Business Professionals (1 edition). Hoboken, New Jersey: John Wiley & Sons Inc.

Swires-Hennessy, E. (2014). Presenting Data: How to Communicate Your Message Effectively (1 edtion). Chichester, West Sussex ; Hoboken, NJ: John Wiley & Sons Inc.

Translated and adapted from “Ricerca sociale con R” (chapter 5 “I grafici”)
Fotografia: Library of Congress Catalog:


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