Understanding Sankey Charts: A Visual Guide to Tracking Flows and Quantities in Data
Sankey charts are a valuable visual tool for understanding, analyzing, and communicating complex data flows and associated quantities. These charts are named after Captain Matthew Henry PH Sankey, who developed them as a way to illustrate the energy and waste flow in various steam engines in the mid-19th century. Since then, the concept of Sankey diagrams has evolved, becoming an integral part of modern data visualization.
## How Sankey Charts Work
Sankey charts consist of a series of arrows or bands that branch out and link different data categories. The width of each arrow or band indicates the magnitude of the quantity flowing between the categories, making it easy to see where the largest flows occur. This flow can illustrate many types of data: material, energy, money, population, or in web analytics, page interactions, among others.
## Components and Features of Sankey Charts
### 1. Nodes
Nodes represent the origin and destination of the flow within the chart. They can be labeled uniquely to indicate the specific category for the data being flowed. For example, in a financial Sankey chart, nodes could denote the source (e.g., revenue from different sales channels), intermediate financial processes (like costs or taxes), and the end destination (for example, net profit or cash reserves).
### 2. Links or Arrows
Links connect the nodes, showing the paths the flow takes. The thickness of the lines signifies the volume or magnitude of the flow. In some charts, a darker or lighter shade of the line color might also express additional attributes, such as the direction of the flow or its type (positive, negative, etc.).
### 3. Totals
To understand the flow throughout a Sankey chart, it is crucial to view the “total” flow, which shows the cumulative quantity entering and leaving each node. These totals can provide insight into the overall scale of the data being represented.
## Example Use Cases
### 1. Energy Consumption
An energy Sankey chart could illustrate how energy is consumed in a household, workplace, or region. It would show inputs from various sources (electricity from the grid, natural gas, renewable sources, etc.) and where the energy goes (heating, electricity for appliances, lighting, etc.), allowing stakeholders to identify major energy usage patterns and potential conservation opportunities.
### 2. Web Analytics
In digital marketing and web analytics, Sankey charts can visualize user journeys on a website. This includes tracking how users navigate from one page to another or interact with different features, helping identify entry and exit points, frequently used paths, and areas with high bounce rates.
### 3. Financial Management
Organizations can use Sankey charts to illustrate the flow of assets or money within their enterprise. By mapping how funds move through various departments—such as from revenue collection, through expenses, payroll, and to the net profit—it becomes easier to assess financial health, manage budgets, and control costs.
## Advantages of Sankey Charts
– **Reveals Complex Patterns:** Sankey charts excel at uncovering intricate patterns and relationships that might otherwise be hidden within voluminous raw data.
– **Facilitates Comparison:** By comparing the proportions and volumes of flows across different time periods or scenarios, users can observe trends or anomalies readily.
– **Enhances Communication:** A well-designed Sankey diagram can dramatically improve the understanding of non-expert audiences by simplifying complex data into a visually intuitive format.
– **Insight into Interdependencies:** The visual representation makes it apparent how distinct components of a system or process are interconnected, offering valuable insights into how changes in one part might impact others.
## Creating Your Own Sankey Diagram
### Tools and Resources
– **Online Tools**: Canva, Easely, and Visme offer templates and tools to create basic Sankey diagrams with minimal design knowledge.
– **Software Packages**: Programs like Microsoft Power BI, Tableau, and R (with packages like iSankey or ggsankey for ggplot2) provide advanced features and flexibility in creating detailed, customized Sankey diagrams.
– **Custom Programming**: For more complex needs or unique data structures, programmers may develop custom solutions using JavaScript libraries (e.g., D3.js) or Python libraries (like Plotly or Matplotlib).
In today’s data-driven world, Sankey charts provide a powerful tool for organizations and analysts to better understand complex systems and processes, from energy management to e-commerce analysis. By leveraging these diagrams, professionals can uncover insights, optimize operations, and communicate findings effectively to stakeholders.
