Sankey charts, a type of flow diagram, are a remarkable visual tool for depicting the distribution of material, energy, or other types of flows. While they may appear complex at first glance, once you understand the basics, they reveal a wealth of information about the dynamics of systems, especially in the fields of logistics, resource allocation, and infrastructure. This beginner’s guide will help you navigate Sankey charts from the ground up, demystifying their structure and helping you interpret the complex data they reveal.
### Understanding the Basics
#### What’s a Sankey Chart?
Visualize a stream of water flowing through a network of interconnected pipes of varying sizes. This is the essence of a Sankey chart—each bar or “pipeline” represents a specific flow, and the width of the bar indicates the magnitude of that flow. The process is straightforward, but the visual representation can be intricate when displaying real-world data.
#### Key Components
– **Flow Streamlines:** The lines that indicate the flow between elements or entities.
– **Node:** A structure that the flows connect to. In a Sankey chart, nodes are typically the sources (entry) and destinations (exit) of flows.
– **Arrows:** Represent the flows in the system, and their width reflects the amount of the flow.
– **Bends and Branches:** Show the divergence and convergence of flows.
– **Labels:** Identify the elements within the chart, like the materials or energy sources being measured.
### Crafting Your Sankey Chart
#### Step 1: Define Your Objective
Start by clarifying what you want your Sankey chart to represent. Whether you are interested in the energy flow within a factory or the transportation of goods through a country, be specific about the system you are studying.
#### Step 2: Gather Your Data
Collect detailed data that includes the quantities of all flows and the connections between them. For instance, if you are mapping the energy flow within a complex system, you would need to know how much energy is used for each process and how it is transformed.
#### Step 3: Determine Flow Magnitudes
The width of the arrows indicating these flows is proportional to their magnitudes. Be sure to scale your data appropriately, so that even the smallest flows are visible but not clutter the chart.
#### Step 4: Design Your Nodes and Streams
Layout your nodes, making sure they are positioned logically to reflect the information you want to convey. Create the streamlines connecting your nodes based on the data you have gathered.
#### Step 5: Validate and Iterate
Sankey charts often require adjustment. As you complete your design, always go back and check for any discrepancies or areas that may be confusing. Be prepared to iterate on your visualization.
### Interpreting Sankey Charts
#### Reading the Flow
The arrows in a Sankey chart provide visual cues on the amount of material, energy, or information being moved. Widest segments show the largest flows.
#### Detecting Hot Spots
Sankey charts can help identify “hot spots” where a vast amount of flow converges or diverges. By highlighting these areas, you can focus additional study or optimization efforts there.
#### Analyzing Efficiency
One of the most significant advantages of Sankey charts is their ability to examine the efficiency of processes. By comparing the widths of the arrows, you can infer how much “value” is lost or conserved during a flow.
#### Comparative Analysis
Compare Sankey charts of different systems to assess which one is more efficient or contains less waste. They are especially useful when comparing the performance of multiple systems within the same context.
In conclusion, Sankey charts are powerful tools for analyzing and understanding flow and transportation dynamics. Whether you are analyzing a manufacturing process, a traffic system, or a logistics network, the step-by-step approach outlined here will set you on the path to creating and interpreting Sankey charts like a pro.
