Sankey charts have long been an under utilized, yet powerful visualization tool, especially useful for displaying complex flow and transport systems. Whether you’re presenting the inner workings of a company’s supply chain, the energy flow through a process, or the distribution of water in a hydrological system, Sankey charts can communicate this information effectively with a unique, intuitive style. In this complete guide, we will delve into what Sankey charts are, how they are constructed, and how you can create effective flow and transport visualizations that convey your message clearly and memorably.
### What is a Sankey Chart?
To understand Sankey charts, we must first establish their purpose: they provide a clear and concise visual representation of the flow of materials, energy, or resources through a system. The distinctive aspect of a Sankey chart is that it displays the magnitude of the flow using the width of the arrows that represent that flow, allowing for an at-a-glance comprehension of the quantities involved.
### Sankey Chart Elements
– **Flow:** Represented as an arrow with a starting and ending point.
– **Nodes:** Nodes, or junction points, are where flows enter or exit the system, and are often depicted as circles or squares.
– **Channels:** Channels are the connections between two nodes and represent the flow between them.
– **Sankey Boxes:** These boxes can be added to label the channels or to draw focus to specific areas of detail.
### Creating a Sankey Chart
#### 1. Identify the System
Decide what system you are trying to analyze and understand its components, inputs, and outputs. For example, if you are looking at a water system, identify the sources of water, its flow, and where it is used or wasted.
#### 2. Define the Flow
Quantify the flow in the system. The amount of flow is typically measured in volume, mass, or energy, depending on the context.
#### 3. Plot Nodes
The nodes are the key junction points in your system—plot them at strategic locations that accurately represent the system design.
#### 4. Draw Channels
Connect the nodes with channels according to the flow of your system. The width of each channel should reflect the relative magnitude of the flow.
#### 5. Add Labels and Sankey Boxes
Label each node and channel as needed so viewers can easily understand what they represent. Sankey boxes are optional, but they can provide a visual emphasis on important data.
#### 6. Formatting
Choose a color scheme that reflects the information being presented and that is distinct and easy to interpret. Be mindful not to have too much clutter by using white space effectively.
### Effective Visual Techniques
– **Consistent Width:** Ensure the width of the arrow consistently reflects the amount of flow regardless of the direction.
– **Avoid Redundancy:** Overlapping or crossing lines can confuse readers; be mindful to maintain a clear visual hierarchy.
– **Scale:** Use logarithmic scales for y-axes if you need to show large differences in flow magnitude, so the chart remains readable.
– **Consistency:** Be consistent with your direction and the handling of nodes and channels.
### Conclusion
Sankey charts are invaluable for their ability to convey complex system information in a way that is both informative and accessible. By following these steps and best practices, you can create Sankey charts that are effective, visually compelling, and above all, informative. It takes practice to perfect the art of crafting compelling Sankey visualizations, but with this comprehensive guide, you are well on your way.
