Visible Notion and Knowledge Visualization
Within the subject of information visualization, why will we care a lot about visible notion? Does it actually matter when creating charts and graphs? The reply is a powerful sure; it does matter, and hopefully this one quite simple instance will show why it issues.
Beneath are two chart legends taken from information visualizations accomplished in Tableau. The primary is from an information visualization accomplished by Kelly Martin, and the second is from my very own crime visualization, each out there for obtain on Tableau Public. First, let me emphatically state that I’m not choosing on Kelly. The truth is, my major purpose for utilizing her visualization for instance is to offer a further shout out to her for her extremely well-done visualization on hen strikes that may be discovered here.
In each of those examples, discover how the legend bar seems to be a distinct measurement at every finish. The sunshine ends seem like wider than the darkish ends. The phantasm right here is that the bar is getting narrower as our eyes transfer from the left aspect of the bar to the suitable aspect. They’re really true rectangles, however our minds are enjoying a trick on us. On this case, the grey border across the legend seems as a border on the left aspect, however on the suitable aspect, the border blends into the darker colour of the legend which makes it seem like it disappears.
This can be a very delicate and minor instance, however this is without doubt one of the causes that information visualization consultants keep away from gradient results and pay such shut consideration to the usage of colour. On this specific case, the sequential colour scheme is used on a chart or map and that is the legend, so the gradient colour isn’t used for an impact, however relatively encoding a variety of information, going from gentle for the low worth to darkish for the excessive worth.
There are a number of options to fixing this specific subject. One simple methodology is to use a darker border to the legend. Within the instance under, the black border strikes the mixing impact additional to the suitable aspect, due to this fact decreasing the impact of the phantasm.
This helps fairly a bit, nevertheless it doesn’t remedy it utterly. Within the authentic instance which is the default in Tableau, the sunshine grey border disappears in the midst of the bar and blends into the bar colour. Utilizing a black border strikes that mixing to the suitable aspect of the legend.
Within the subsequent instance, there’s a darkish border round a light-weight border, and the visible notion downside is solved. Discover on this instance there seems to be white area on the suitable aspect of the legend that blends in on the left aspect. The double border helps visualize an equal measurement legend as the attention strikes from left to proper.
Beneath is a visible comparability of the three choices aspect by aspect:
Each of those examples had been taken from Tableau Public Visualizations, and sadly we’ve got restricted choices in Tableau for fixing this specific downside. There are not any border choices for the bar in a legend, not to mention the management of a double border. Within the examples under we will help resolve the visible notion downside through the use of a pseudo border. This feature makes use of one other precept of visible notion known as the Gestalt Precept. Our minds will shortly draw conclusions from incomplete info, on this case forming a rectangle. By including a partial border our minds will understand sufficient of a border across the legend and supply a baseline working parallel to the underside of the legend which minimizes the visible notion downside that happens within the default legend.
This partial border is completed by:
1.) underlining the legend title
2.) including a vertical object with a border
3.) setting the float order to again
Observe: you will be unable to make use of a static picture (the final possibility) if the visualization is interactive and the chart or map is dynamic inflicting the values to replace. Additionally, even when the visualization shouldn’t be interactive, this might trigger an issue if the underlying information ever modifications and the visualization is refreshed.
The legend examples above contain a really small object, however this subject additionally applies to different points of information visualization. Look at the bar chart under. Along with the issues outlined above, discover the heavy emphasis given to the left aspect of the bars whereas the suitable sides disappear into the white background making it very tough to find out the size of the bars and make fast comparisons.
Sure, we might additionally remedy a few of these points by including a border across the bars, however on this instance, the gradient colour scheme is including no worth. Within the legend, we wanted the sequential colour scheme to distinguish between high and low, however that isn’t needed on this bar chart. Additionally, including a border nonetheless received’t assist the heavy emphasis that’s positioned visually on the left aspect of the bars. On this case, as with most charts like this, utilizing a typical fill with out gradient is greatest.
I hope you discover these examples useful in outlining why visible notion is so necessary within the subject of information visualization. If you need to study extra about visible notion, I extremely advocate the guide Primary Imaginative and prescient: An Introduction to Visible Notion by Robert Snowden, Peter Thompson and Tom Troscianko.
As all the time, if in case you have any questions be at liberty to e-mail me at Jeff@DataPlusScience.com
Jeffrey A. Shaffer
Observe on Twitter @HighVizAbility
Edited by Breanne LaCamera 11/9/2014 and posted 11/13/2014