Sankey diagrams are a unique type of flowchart that depict the transfer, movement, or transformation of energy, resources, people, or other entities. They are named after English engineer William D. Sankey, who introduced them in the late 19th century to visualize the steam engine systems. Though they may initially seem complex, Sankey charts can offer valuable insights into the efficiency and distribution of various processes. This beginner’s guide will help you understand the basics of Sankey charts so you can interpret them like a pro.
**What Are Sankey Charts?**
Sankey diagrams are made up of horizontal branches that represent the energy or substance flow and their associated paths. These paths are usually scaled such that the width of the branch is proportional to the magnitude of the flow it represents. By convention, the size of the arrows indicates the amount of material or energy being transferred. You might find Sankey charts used to visualize economic data, engineering processes, or even software performance.
**Key Features of Sankey Diagrams**
1. **Directional Flow:** Sankey diagrams are always directional, indicating the flow of materials or energy from one point to another.
2. **Flow Magnitude:** The width of the flowing path corresponds to the quantity, often measured in mass, volume, cost, or energy, passing through it.
3. **Flow Losses:** The diagrams are not limited to perfect processes; they can also illustrate losses and inefficiencies with wider, shaded areas, so you can see where flow is reduced.
4. **Consistency of Flow:** Each item in a Sankey diagram enters a particular path at the same location, and, generally, each item leaves it at the same location along the y-axis, making them ideal for illustrating processes with consistent flow.
**How to Read a Sankey Chart**
1. **Identify the Process:** Understand the process being depicted to interpret the diagram accurately. What is the primary input and output of the process?
2. **Follow the Flow:** Observe how the flow expands and contracts to represent larger quantities and then narrows down as the material is processed or lost.
3. **Look for Losses:** Notice the shaded regions that indicate inefficiencies or losses. These are crucial for understanding the process’s overall performance.
4. **Measure Width:** Take note of the width of the paths: wider paths represent higher flow rates, while narrower paths stand for lower flow rates.
**Using Sankey Charts**
1. **Data Preparation:** Ensure that your data is well-structured and accurately represents the flow of materials, energy, or people through the process or system.
2. **Choosing the Software:** There are numerous software tools available for creating Sankey diagrams, such as Sankey Studio, Visualize, or SigmaPlot. Choose one that aligns with your skills and requirements.
3. **Labeling:** Proper labeling is essential for reader comprehension. Label nodes and paths clearly, and provide explanations where necessary.
4. **Comparison:** Use Sankey charts to compare different processes or variations of the same system to understand how they differ and identify areas for improvement.
5. **Iterate:** Sankey diagrams are not static; they can be refined and updated based on new data or insights.
Understanding Sankey charts can provide a wealth of information about complex processes. As your skills and knowledge grow, you’ll appreciate their ability to reveal efficiencies, streamline operations, and guide decision-making in various fields. By following this beginner’s guide, you’re on your way to decoding the power of Sankey diagrams!
