# Unraveling Complexity with Sankey Charts: A Visual Guide to Flows and Connectivity
In the realm of data visualization, Sankey charts stand as a powerful tool to decode complex relationships and flows within a dataset. Pioneered and popularized for their ability to represent material, energy, or data flows, Sankey charts effectively transform overwhelming, dense information into digestible, insightful graphics. This article aims to illuminate the principles of Sankey charts, their application, and provide an in-depth guide on how to create them using simple step-by-step instructions.
## What are Sankey Charts?
Sankey charts, named after their inventor, Captain Matthew Henry Phineas Riall Sankey, who developed them to visualize the energy exchanges on the steamship “SS Great Britain” in 1898, are a type of flow diagram. These charts are unique for their emphasis on the movement and the volume of connections between data points. Typically, each flow is represented by a line whose thickness visually represents its flow quantity, making it easy to highlight the most significant flows within the dataset.
## Elements of a Sankey Chart
### 1. Nodes:
These are the endpoints of the relationships you wish to visualize. Nodes are usually depicted as distinct shapes (circles, squares, ellipses, etc.) and should be named to represent the categories at their endpoints in the flow.
### 2. Links & Arcs:
Links or arcs connect the nodes in a sankey diagram, denoting the flows between different categories or variables. The width of these links is proportional to the volume of data being represented, making it an excellent tool for emphasizing key patterns.
### 3. Values:
Values are assigned to the links either through labels or arrows that indicate the flow quantity. This might represent energy usage, material flow, traffic, or any transfer of data or resources between categories.
### 4. Background Grid:
Optional elements, such as a background grid, can add another layer of information or aesthetic appeal to the chart. It is often used in conjunction with labels to improve readability.
## Applications of Sankey Charts
### Business Strategy
In business strategy, Sankey charts are used to represent processes, from customer journeys to production flows, and to highlight where the largest losses or gains occur.
### Energy and Sustainability
In energy and sustainability, Sankey charts are utilized to illustrate how energy is produced, consumed, and lost, revealing inefficiencies and opportunities for improvements.
### Epidemiology
In epidemiology, Sankey diagrams can be used to track the spread of diseases, showing pathways that might indicate points of high infection and the effectiveness of interventions.
### Web Analytics
In analytics, such as web visit data, Sankey charts can visualize user navigation on websites, offering insights into which links or pages are most frequently visited and their inter-relationships.
## Creating a Sankey Chart
### Tools to Use
#### 1. Microsoft Excel
Excel offers a Sankey chart template under the “Insert” > “Recommendations” feature, which works well for simple datasets. Use Excel’s data preparation capabilities to structure your data before creating the chart.
#### 2. Tableau or PowerBI
Both Tableau and PowerBI provide robust options for creating intricate sankey diagrams. They offer extensive customization and advanced features, ideal for complex datasets or businesses requiring detailed visual analytics.
#### 3. Gephi
Gephi is a network visualization software that not only supports Sankey-style diagrams but adds a dimension of topology analysis, making it suitable for more sophisticated data exploration.
### Steps to Create a Sankey Chart
**Step 1: Prepare Your Data**
Gather and organize your dataset into a structured format with three columns: the source category, the target category, and the flow value.
**Step 2: Choose Your Software**
Select the tool that best fits the complexity and volume of your data (Excel, Tableau, PowerBI, or Gephi).
**Step 3: Import Data**
Input your dataset into the chosen tool and ensure it is correctly formatted.
**Step 4: Configure the Chart Type**
Navigate to the chart creation tool within your chosen software (Excel’s chart creation wizard, Tableau’s or PowerBI’s visualization editor, or Gephi’s graph editor) and select Sankey chart.
**Step 5: Customize Your Chart**
Adjust the layout, formatting, and tooltips to enhance readability and to effectively communicate the underlying data.
**Step 6: Analyze and Refine**
Inspect the chart’s visual representation of the data flow. Adjust dimensions, link sizes, and colorations as needed to make the chart more intuitive and impactful.
## Conclusion
Sankey charts represent a powerful method for visualizing complex data flow and connecting relationships through a graphical interface. By following the structured steps outlined, you can effectively translate intricate datasets into clear, actionable insights. Regardless of the tool you choose, the key remains in the preparation of your data and the customization to ensure your chart resonates with the unique narrative of your flow data. Whether used for strategizing business decisions, understanding scientific data, or improving public health policies, Sankey charts prove to be an indispensable tool in the data analyst’s arsenal.
