Sankey diagrams are an excellent tool for illustrating the flow of energy, resources, data, or any quantity through a system and they’ve gained popularity for their unparalleled ability to convey complexity succinctly. Even so, they can be somewhat daunting for beginners. This guide is here to demystify the process and help you understand the basics of Sankey charts so that you can start creating them like a pro.
**What is a Sankey Chart?**
A Sankey diagram is a type of flow diagram that methodically identifies and visualizes the flow of material, energy, or costs within systems at various scales. Originally used by miners, Sankey diagrams have been employed across many fields, such as process management, logistics, and environmental systems, thanks to their ability to break down complex data into manageable, visually appealing formats.
**Understanding the Anatomy of a Sankey Diagram**
1. **Flow Arrows**: These are the primary visual elements of a Sankey diagram. They represent the flow of energy, material, or other forms of quantity from one point to another. The width of an arrow varies depending on the quantity it represents: wider arrows denote larger quantities of flow.
2. **Horizontal Axis**: Typically called the process or system axis, this is where the various process components and connections are listed.
3. **Vertical Axis**: Often referred to as the flows axis or the energy axis, it represents either the quantity of the flow under consideration or the energy at a specific point in a process.
4. **Sankey Units**: Each Sankey diagram must use a common unit of measurement to ensure accurate comparisons across different flows, though the units often may not be visible.
**Key Features of Sankey Diagrams**
1. **Efficiency and Energy Loss**: Sankey diagrams often highlight inefficiencies by demonstrating how much energy or resource is lost (usually through the width of the arrows).
2. **Scale Balance**: Although a Sankey diagram can sometimes be tricky to proportionally size all of its arrows to depict the true scale of values, it makes up for that by illustrating the distribution of fluxes in a visually intuitive way.
3. **Legends**: A legend is essential for explaining what the different colors or symbols represent in your Sankey diagram.
**Creating a Sankey Chart**
1. **Define Your Objective**: What kind of system will your Sankey chart depict? What information are you trying to convey?
2. **Gather Data**: Collect flow data, identifying where resources enter and exit the process you’re studying. It’s important to have precise and accurate data for effective diagram creation.
3. **Choose the Right Software**: There are many Sankey diagram tools for different platforms including Excel, Gephi, MATLAB, ProcessOn, and Python libraries like Matplotlib and Plotly.
4. **Design Your Layout**: Begin by drawing the main flow arrows on your diagram, then work out the points at which they should split or merge. Balance the complexity of your chart with a degree of clarity to avoid overwhelming the audience.
5. **Fine-Tune Details**: Add labels and scale indicators. Adjust the width of arrows according to your data, using the software’s scaling tools. Remember that too many different sizes can cause disorientation.
**Conclusion**
Sankey diagrams are powerful tools for data visualization, but it takes time and practice to create diagrams that are both informative and aesthetically pleasing. By understanding the basic principles, you’ll be on your way to crafting clear and effective Sankey charts that facilitate a deeper understanding of your data and processes. As with any skill, mastering the fundamentals is the first step to becoming proficient. Start with simple models, and as you gain more confidence, you can gradually tackle more complex systems. Happy charting!
