Sparklines and Heatmaps – Using heatRate To Make Effective, Concise Visualizations
The main function of data visualization is to help us better understand the concept of a data set quickly. When done effectively, data visualization can look organic and beautiful, but the primary goal is to help the viewer to consume and understand the gist of the data quicker than if he/she were looking at the sum of its parts.
Rating systems are a great example of where we could do better with data visualization. As Goodfil.ms mentioned last week in a post about rating systems, 5-star rating systems are broken.
A typical rating system should convey information quickly to a user as they browse through many entities on a screen. The 5-star rating system does do this, but it only shows a mean, not an entire dataset that the mean is derived from. Amazon.com does a breakdown of ratings and shows the context and relationship between all of the ratings for a product but they are too verbose to be put into a browsing view; they simply take up too much space.
The problem: we need to show detailed information of a dataset in a small space in a way that can be understood easily and quickly.
Plenty of research has gone into sparklines, which does exactly this – cram detailed information into a small space. Sparklines have been deemed pretty successful in applications, especially when surrounded by a lot of content. A study published in the IEEE Transactions on Visualization and Computer Graphics in 2010 showed that tag-cloud using sparklines resulted in faster task times, fewer errors, and was more preferred than its stacked-bar and multi-line chart counterparts.
Ok, great, a sparkline visualization meets our needs for space and can be an effective conduit, but how are we going to actually show the data we have?
Typically we think of heatmaps working really well in spatial relationships, but they've also been attributed to working extremely well when reviewing large datasets. Specifically, heatmaps can be used to find clusters and correlations from large datasets to those with only a few data points, such as 5-star ratings.
Heatmaps and sparklines are two good solutions to the problems with displaying rating results. That's why we created heatRate; a jQuery plug-in which takes a simple 1-dimensional array and creates a CSS gradient heatmap that displays the data on any HTML element you'd like.
You can keep the visualization in-line with your other elements but still see details you might otherwise miss on the standard 5-star rating visualization. heatRate has various options you can adjust to change contrast and the overall look of the heatmap gradient altogether. It works by employing HSLa, so you can choose to have values change based on hue, saturation, or lightness.
heatRate would be a good choice for you to use anywhere that you might have varied values in your data, even outside of the scenario of a rating system.
Give it a try and share your feedback with us! We'll be working on new features for this project in the coming weeks. We're obsessed with finding better ways to visualize data.