Sankey diagrams, also known as Sankey flow diagrams, have long been employed for depicting the flow of energy, materials, or costs within a system. While complex in their design, they offer an invaluable way to illustrate the interconnections and dynamics of a process at a glance. This comprehensive guide will walk you through the creation and interpretation of Sankey charts, helping you harness their power in your own work.
### Understanding the Basics
Before we delve into creating and interpreting these visualizations, it’s important to grasp the foundation of Sankey charts.
#### What is a Sankey Chart?
A Sankey chart is a flow diagram where a directed, colored ‘arrow’ (or several arrows parallel to each other) on a two-dimensional field shows the quantity flow of material (or sometimes energy, money, or people) from one element to another. The width of the arrow represents the amount of material or energy of the flow.
#### Features of a Sankey Chart
– Horizontal and vertical arrows represent the movement of ‘energy’ or ‘material’.
– The thickness of the arrows decreases as they approach the destination, representing the loss of energy or materials.
– Connections can join arrows at any size without any special significance.
– The field often extends into the background, with a label representing the total amount of items being viewed.
– Nodes or points of entry and exit are often represented by circles, boxes, or other shaped symbols.
### Creating Sankey Charts
To create a Sankey chart, you typically follow these steps:
#### 1. Identify Your Data
Gather your data on the flow you wish to depict, considering input, processes, and output.
#### 2. Determine the Structure
Decide on the nodes (the points of entry and exit) and connections. This structure will inform your chart layout.
#### 3. Select the Appropriate Tool
Choose a software tool or programming library that supports Sankey chart creation. Some popular options include Microsoft Excel, Power BI, R’s ggsankey package, and Python’s Sankeyplot.
#### 4. Create the Sankey Chart
Input your data and configure the tool’s settings. This often involves defining the number of nodes, setting the type and amount of flow for each arrow, and indicating how many connections should be drawn.
#### 5. Customize the Visual Elements
Adjust the width and direction of the arrows, add labels, and choose colors that are clear and distinguishable to match your data’s structure.
#### 6. Validate the Representation
Double-check the accuracy of your representation. Ensure that the flow paths are logically connected and the thickness of the arrows reflects the relative amount of flow.
### Interpreting Sankey Charts
To truly leverage the power of Sankey charts, the following interpretation guidelines are essential:
#### 1. Flow Direction
Observe the flow direction and understand which processes are the primary input and output points.
#### 2. Flow Magnitude
Analyze the thickness of the arrows to determine the magnitude of the flow at different points of the system.
#### 3. Energy or Material Loss
Focus on how the width of arrows decreases along the flow path—this indicates where energy or materials are being lost or transformed.
#### 4. Efficiency
Look for opportunities for improvement by identifying bottlenecks or inefficiencies in the system, such as particularly thick arrows or sudden shifts in flow direction.
#### 5. Contextual Information
Consider any additional information about the system, such as the source and destination of the flow, and how it may influence your interpretation.
#### 6. Comparisons
When using multiple Sankey charts, compare and contrast the visualizations to uncover trends or anomalies.
By understanding these basics, you’re well-equipped to create and interpret Sankey charts that provide critical insights into the dynamics of your chosen processes. Whether for energy efficiency analysis, supply chain management, or process automation, Sankey charts offer a clear, informative means to illustrate complex systems in an accessible format.
