I've commented in the past about the important role that text plays in data visualization: in short, it helps to make the information you provide more accessible to your audience. But where should you place your text for it to best play its role? When it comes to chart and axis titles and legend, my recommendation is to left uppermost justify.
I frequently see chart and axis titles center-aligned and the legend placed to the right of the data it describes. Many standard tools default to this. I favor left uppermost justifying over center-title-alignment and righthand-legend-placement due to two reasons:
- Center alignment looks messy: center alignment doesn't create a clean line on either the left or the right, so text is left visually hanging.
- Your eye hits the left uppermost space first: in Western cultures, most people read left to right, top to bottom*. This means if you left uppermost justify your graph title, legend, and axis titles, your audience's eye hits how to interpret what they're looking at before they get to the data.
*I'm frequently asked the question how this changes in cultures reading in other directions: the small sample I've posed this question to have said that when it comes to business, the Western style prevails since so much international business is conducted in English. Please leave a comment with your thoughts if you have insight on this!
What I mean when I say "left uppermost align" when it comes to graph titles and legend is:
- Graph title (+subtitle, if applicable) are positioned above graph and left-aligned.
- Legend is placed above graph (below title/subtitle) and left-aligned.
- y-axis title is aligned with topmost y-axis label.
- x-axis title is aligned with leftmost x-axis label.
Here's a quick look at what a typical graph looks like with default text alignment settings compared to when we follow this tip:
Personally, I steer clear of center alignment almost always in favor of left- or right-alignment. Outside of titles and legends, whether to left- or right-align your text comes down to the layout of the visual: sometimes right-alignment makes sense, for example in a horizontal bar chart you should right-align your y-axis labels so that funny spacing isn't created between the labels and the data. When in doubt, try aligning a couple of different ways and see what looks best: trust your eye or solicit input from a colleague.
Note: the Excel template to create the left uppermost chart above can be downloaded here.