Plotting Flows Clearly: A Visual Guide to Sankey Charts

Understanding the intricate flows between different quantities or the distribution of data between multiple systems can be challenging. Traditional bar charts, pie charts, or line graphs fall short in depicting complex, multi-layered flow data. This is where Sankey charts come into play, offering a clear, intuitive, and engaging way to visualize complex systems or large flows of data. In this visual guide, we’ll explore how to create Sankey charts, their applications, and how they provide a comprehensive view of data flows.

Understanding Sankey Charts

Sankey diagrams, named after its inventor, Irish scientist Mark Moncrieff Sankey, were initially used to depict steam engine efficiencies in the late 19th century. Today, they are widely used across various fields, including energy, economics, data analysis, and environmental research, to visualize complex data sets.

A Sankey chart is an effective way to represent the flow of energy, goods, or information between processes, categories, or phases. It consists of several streams (or links), each with a width proportional to the quantity it represents. This proportional width is often based on the quantity’s percentage of the total inflow into the system or outflow from a system.

How to Create a Sankey Chart

Gather Your Data

The first step in creating a Sankey chart is to gather your data. This data should be in a tabular form that includes the starting points (sources), destinations, and the quantity flowing between them.

Prepare Your Data

Once you have your data, you need to prepare it for visualization. This typically involves rounding and grouping data points to simplify the chart and to make the visualization more understandable.

Choose a Tool or Software for Sankey Chart Creation

There are several tools and software available for creating Sankey diagrams, including Microsoft Excel, Tableau, d3.js (a JavaScript library for creating and manipulating documents based on data), and Python libraries like Bokeh or Streamlit. Choose a tool based on your technical skills and the complexity of the Sankey chart you’re aiming to create.

Create a Sankey Chart

Follow these steps in your chosen tool:

Identify Your Inputs and Outputs: Determine where the flow starts and ends. These will be your leftmost and rightmost streams, respectively.
Divide Your Table: Align your data points by their inputs and outputs, creating separate sections.
Calculate the Widths: Assign widths to your streams. The width of each stream is proportional to the value of the data flow it represents. You can use a simple formula to calculate how the width scales with respect to the data flow.
Create the Sankey Diagram: Follow your tool’s instructions to draw the streams between the nodes. Ensure that the nodes (where the streams start and end) are labeled correctly.

Applications of Sankey Charts

Sankey charts are versatile and can be used across various fields. Here are a few notable applications:

Environmental Data: They are excellent for visualizing energy flows within buildings or power systems.
Economic Flows: Analyzing the distribution of wealth, resources, or trade flows between countries or over time.
User Behavior Analysis: Understanding how users move through a website or app, starting from homepage to various sections.
Complex Business Processes: Visualizing the movement of products, money, or services between different stages of a business process.

Conclusion

Sankey charts are a powerful tool for visualization, offering a clear and engaging way to understand complex data flows. By following the steps outlined in this guide and choosing the right tool, you can create insightful and informative Sankey diagrams for your projects. Whether you’re analyzing energy use, tracking user behavior, or visualizing economic flows, Sankey charts provide a rich and detailed overview of your data, making them a valuable asset in data visualization.

SankeyMaster

SankeyMaster is your go-to tool for creating complex Sankey charts . Easily enter data and create Sankey charts that accurately reveal intricate data relationships.