A stream graph is a beautiful variation of a stacked area chart. The difference is in the placement of the areas – they are not fixed to the traditional axis line. Instead, they are placed around the central axis. This creates a visualization that resembles a river-like stream.
The stream's shape, made up of peaks and troughs representing varying values over time, can also indicate seasonal patterns. However, the primary purpose of this chart is to show an overall view of the part-to-whole proportions and relations between values in dynamic, without focusing on a detailed representation of the values.
Streamgraph was developed recently by Lee Byron and made popular by the New York Times publication of the history of movies’ box office revenues “Ebb and Flow of Movies” by Mathew Bloch, Lee Byron, Shan Carter, and Amanda Cox.
In contrast to traditional stream graphs where area borders are smoothed, stepped streamgraphs present each area range as a rectangle, similar to a stacked bar chart. This format provides a more precise view of each entry.
A stacked column chart can be an alternative for a stepped streamgraph as it has the same visual elements – stacked rectangles. However, the main difference lies in the positioning of the axes. A stacked bar chart uses the standard X and Y axes, whereas a stream graph centers around a central axis.
A good chart to use if a stream graph appears too complicated. Line charts allow for a simpler presentation of the data, making them more easily comprehensible for a broader audience. Compared to stream graphs, line charts are more conventional and are used more frequently in data visualization.
This chart can serve as an alternative to stream graphs for displaying percentage distribution. One key difference between them is their orientation - the violin plot is vertical while the stream graph is horizontal. The violin plot is suited for showing one series, whereas the streamgraph is used for visualizing multiple series.
When it comes to coloring stream graphs, there are typically two main approaches. The first is by using color to distinguish categories, assigning each one a distinct hue. This method works well as long as the number of categories is relatively small (typically around 6 to 10, depending on the specific case). The second option is to color groups with the same hue, but vary the saturation and lightness for each individual category within those groups. This technique is particularly useful when comparing two or more big categories.
To draw attention to certain categories in a stream graph, one effective technique is to highlight these areas while using a neutral color for the rest. Our brain is wired to notice deviations instantly. This can be done, for example, by applying changes in size, movement, or color. This way, highlighting a specific area will help catch the reader’s eye immediately.