Deconstructing Process Flows: A Comprehensive Guide to Creating and Interpreting Sankey Charts
Sankey charts are a type of graph that are particularly useful for visualizing the flow of entities, materials, energy, or data from one point to the next. Named after Captain Matthew Henry Sheppard Sankey, an English engineer who developed this type of diagram around the 1860s, these charts have become an increasingly popular element in data storytelling. Given their ability to represent complex flows clearly and concisely, they help in understanding how quantities are distributed, transformed, and interact within systems.
### Understanding the Basics of Sankey Charts
Sankey charts consist of nodes (representing points in the flow) and bars (links between these nodes) with area proportions reflecting the quantities being transferred. Here’s a breakdown of the key components:
1. **Nodes**: The starting and ending points of the flow, typically used to indicate sources and destinations or classes within a system. Nodes can carry descriptive labels to indicate the nature of the entity involved in the flow.
2. **Links or Bars**: These represent the flow between nodes, connecting them in a way that clearly indicates direction. The width of these bars or arrows is proportional to the magnitude of the flow, emphasizing the most significant paths or transformations.
3. **Arrows**: These indicate the direction of flow. The size and color of the arrows are commonly used to represent magnitude and type of entities or conditions flowing through the system, respectively.
### Step-by-Step Guide for Creating Sankey Charts
#### 1. **Data Collection and Preprocessing**
– Gather data on the different entities involved in the flow as well as the quantities flowing between them at different stages.
– Preprocess the data if necessary, ensuring it’s in a format that can easily be mapped to nodes and links.
#### 2. **Selecting Software and Tools**
– Decide on the software or tools to create the Sankey chart. Popular options include:
– **R (with packages like `sankeychart` or `networkD3)**
– **Python (use libraries like `plotly` or `matplotlib`)**
– **Power BI**
– **Tibame T-SQL** for SQL-based solutions
– Consider the specific features, ease of use, and visualization capabilities of these tools.
#### 3. **Designing the Layout**
– Arrange nodes around the periphery of the chart as they represent the entities involved in the flow.
– Position nodes in a hierarchical or categorical order that makes logical sense for the data and is visually appealing.
#### 4. **Laying Out the Links Bar by Bar**
– Introduce flow between nodes by creating bars that connect corresponding nodes, ensuring the direction is indicated by the position and any arrows.
– Ensure continuity and coherency throughout the chart, and make clear connections between elements without cluttering the visualization.
#### 5. **Adding Dimensions**
– Include additional dimensions such as entity type, flow categories, or temporal aspects (if applicable).
– This might involve using color, size, and/or annotations to differentiate between various aspects of the data.
#### 6. **Review and Refinement**
– Once the initial draft is created, review it for clarity and effectiveness in conveying the flow data.
– Adjust the layout, color schemes, and text to enhance readability and visual appeal.
#### 7. **Deployment and Presentation**
– Integrate the chart into a larger dashboard or presentation as a tool to aid in understanding complex data flows.
– Ensure that the chart is accessible and comprehensible to your intended audience.
### Interpreting Sankey Charts
Interpreting Sankey charts involves several key steps:
– **Identify all nodes**: Understand what each node signifies in the context of the data.
– **Follow the flows**: Trace the bar lines to see how the flows start from one node and end at another, considering the direction and the flow’s width as indicators of magnitude.
– **Analyze the dimensions and annotations**: Look at any colors, sizes, arrows, or labels to understand what they signify, such as specific categories, time periods, or types of flow.
– **Spot patterns and anomalies**: Look for dominant flows, concentrated flows, or unusual patterns that might indicate systemic changes or bottlenecks in the processes being visualized.
### Conclusion
Sankey charts offer a powerful tool for visualizing flow dynamics in a wide array of settings. By following this comprehensive guide, you can create effective Sankey charts that not only illustrate data but also facilitate a deep understanding of complex systems, making this type of chart an invaluable asset in conveying intricate information clearly and efficiently.
