Decoding the Stream of Data: A Comprehensive Guide to Creating and Understanding Sankey Charts
Sankey charts are a type of flow diagram that represent a material’s, energy’s, or other flow quantitatively through a system. They are named after the Scottish engineer, Matthew Henry Phineas Riall “Matty” Sankey, an innovator in energy efficiency studies, who popularized them in the 19th century. In modern applications, Sankey diagrams can depict various data streams like information flow in websites, migration patterns, trade exchanges, or even electricity distribution in power grids.
This article provides a step-by-step guide on how to effectively create and understand Sankey charts, breaking down both the foundational theory and practical techniques involved. Each component of the Sankey chart is further elaborated to foster a comprehensive understanding of the graphical layout and its underlying mechanics.
### Understanding the Components of a Sankey Chart
A Sankey chart comprises three major components:
1. **Nodes**: These represent the nodes or points in the system where the material or energy flows. Nodes can be either inputs or outputs. For instance, in a power grid, a node might represent a nuclear power plant, a hydroelectric dam, or the connection to the national power grid.
2. **Arrows/Links**: These represent the flows of material or energy between the nodes. The arrows depict the direction of the flow, with the source node typically positioned before the arrow and the drain node after it. The arrows are also color-coded for clarity to indicate the material or energy type, for example, green for electricity, red for coal, etc.
3. **Widening and Narrowing of Aesthetics**: The width of an arrow in a Sankey diagram is proportional to the volume of the flow it is representing. Thus, a wider arrow signifies a larger flow, while a narrower arrow indicates a lower flow rate. These wider and narrower segments help visually emphasize where the significant material or energy transfers are occurring.
### Creating Sankey Charts
Creating a Sankey chart involves several steps using various tools:
1. **Data Preparation**: Gather relevant data for your Sankey diagram, including the source nodes, target nodes, and the flow volumes between them. It could be sales figures showing product sales distributions, traffic data mapping website visits across various pages, or energy charts tracking power consumption across different facilities.
2. **Design Selection**: Choose a design tool or software that best suits your needs. Popular options include Microsoft Power BI, Tableau, and dedicated Sankey chart tools like SankeyChart.js or Sankey Diagram Generator. Each tool has unique features, so it’s essential to pick one that corresponds with both your skill level and specific chart requirements.
3. **Data Input**: Import your dataset into the selected tool’s interface. This process typically involves creating categories for your nodes and defining the flow parameters. For instance, if you’re creating a financial Sankey diagram, you’d categorize the nodes by different departments and input the budget transfer values.
4. **Visualization and Customization**: Adjust the layout and design elements according to your preferences. This includes setting node colors, defining flow arrow styles, and adjusting the diagram’s overall aesthetic to ensure it is informative and aesthetically pleasing. Tools like SankeyChart.js provide extensive customization options for the widths of the arrows, colors, and even animation.
5. **Review and Finalize**: Once built, scrutinize the Sankey chart for clarity, coherence, and its ability to effectively communicate the intended data story. Make any necessary adjustments, such as adjusting text sizes, node titles, or chart dimensions to enhance readability and impact.
### Understanding Your Sankey Chart
Understanding a Sankey chart involves assessing the visual story it tells:
1. **Identifying Major Flows**: Start by noting the widest and narrowest arrows. These represent the most significant flows, which are sometimes the areas of interest for analysis.
2. **Deciphering Direction**: The flow of arrows suggests the direction of data flow or material transactions. Understanding these directions helps identify any one-way transfers or significant circulating cycles.
3. **Applying Contextual Insight**: Combine the quantitative aspect of the data with broader industry background to deduce meaningful insights. For example, if a large percentage of your company’s budget flows from R&D to marketing, it could infer that significant investment is being made in marketing initiatives.
By following these guidelines, you can effectively create and interpret Sankey diagrams that offer valuable insights into a system’s dynamics through its data flow. These charts are particularly beneficial for understanding large datasets presented across numerous nodes, making them a powerful tool in data analytics and visualization.
