Sankey diagrams are a unique and effective way to illustrate the flow of energy, materials, or costs through a system, making it easier to understand complex processes and identify areas of opportunity. By visualizing the data flow in a dynamic and informative manner, these diagrams provide a clearer perspective on the efficiency, effectiveness, and interplay of various elements within a system.
### What is a Sankey Chart?
A Sankey chart, named for the engineer and physicist who first used it in the1880s, John Sankey, is a type of flow diagram. Unlike bar or line graphs, which typically measure quantities along one or two axes, Sankey diagrams distribute flow quantities along the axes in order to preserve the scale of flow between the various elements of the system. The width of arrows in these diagrams always increases or decreases with the quantity flowing through them.
This ensures that the amount of the transported or consumed material is proportional to the width of the arrows. The width of the arrows can represent different quantities, such as power, flow rate, or material quantity. Sankey charts are excellent for illustrating many types of processes, such as manufacturing, energy systems, and cost structures.
### Key Characteristics of Sankey Charts
– **Proportional Widths**: The width of each arrow is always proportional to the magnitude of the flow it represents.
– **Integrated with Flow**: Arrows are typically curved along the path of the flow rather than having a constant width.
– **Simplified Scale**: As Sankey charts focus on the flow of materials of energy through a process, they often simplify other variables in the data set to enhance the clarity of the visualization.
– **Interactive Capabilities**: Many web-based or software solutions allow for a degree of interactivity, allowing users to filter data, toggle between different measures, or explore various aspects of the chart.
### Creating Sankey Charts
The method used to create a Sankey chart depends on the tool or software you choose. Here’s a general overview:
1. **Gather Data**: First, you’ll need a dataset that includes data about the flow of materials, energy, or costs throughout your system.
2. **Choose a Sankey Diagram Tool**: There are numerous tools available, ranging from free online services to sophisticated software. Some popular options include Sankey Diagrams by John Nelson, which is a web-based tool; Microsoft Excel, with its Sankey Flow Diagrams; and dedicated software like Gephi or Datawrapper.
3. **Design the Diagram**: Most tools provide a user-friendly interface where you can draw the nodes (the point where two paths intersect) and the paths (represented by the arrows). Once you’ve drawn the structure of your Sankey chart, you can input your data attributes.
4. **Normalize Data**: It’s important to convert the data into a form that corresponds to your chosen units in the width of the Sankey plot.
5. **Adjust the Visual Style**: Customize the appearance of your chart by setting parameters such as width, color, and border thickness.
6. **Analyze the Chart**: Use the Sankey chart to analyze the data; paying special attention to the width of the arrows, which represent the quantity of materials, energy, or money that are moving.
### Benefits of Sankey Diagrams
Sankey charts offer several benefits:
– **Easy to Understand**: They present complex systems and processes in a more intuitive way, making them accessible to people who may not have a background in the technical aspects of the data.
– **Identify Bottlenecks**: Sankey diagrams can promptly highlight the areas of your system where materials, energy, or costs are not used efficiently, which can be crucial for process optimization.
– **Comparisons**: Sankey charts facilitate quick comparisons between different systems or process steps.
Although they are not a silver bullet for all types of data visualization, Sankey diagrams are a valuable tool for presenting flow data, and their effectiveness in communicating complex processes cannot be overstated. With appropriate design and selection of software, creating a Sankey chart is an invaluable strategy for data storytelling and process analysis.
