Flowing Data: Unveiling Insights with Sankey Charts

Sankey charts, named after Captain Sankey, who first used them in 1898 to illustrate the energy efficiency of steam engines, have evolved into a powerful visualization tool for understanding complex flows and data interconnections. Unlike traditional bar charts or line graphs, Sankey diagrams visually represent data flow and transfer between processes, entities, and variables. In this article, we’ll delve into the creation and applications of Sankey charts, exploring how they can help uncover hidden patterns, relationships, and insights from data.

Understanding Sankey Charts

Sankey diagrams are a type of flow diagram where the width of the arrows or lines is proportional to the flow rate or volume of data being represented. They are particularly useful for illustrating data transfer, conversion rates, cost estimates, and the interconnections between different variables. For example, a Sankey chart could represent energy efficiency in a complex system, showing how much energy is lost or transformed at each step.

Creating Sankey Charts

Creating a Sankey chart involves several steps, from data preparation to chart customization. Here’s a simplified guide to get you started:

1. Data Preparation: Gather your data in a tidy format. Generally, you need at least three columns: source, destination, and magnitude (the value you want to represent in the chart).

2. Determining the Widths: Sankey diagrams calculate the width of each arrow based on the data volume flowing through it. This requires organizing your data and calculating the total flow at each end.

3. Visualizing the Data: There are various tools and programming languages you can use to create Sankey diagrams, such as Excel with the help of extensions, Python with Plotly or Bokeh, or R with ggalluvial.

   • Python Example:
     “`python
     import plotly.graph_objs as go
     import plotly.offline as py

     Sample data in a list

     data_list = [{‘source’: ‘Start’, ‘target’: ‘A’, ‘value’: 50},
     {‘source’: ‘A’, ‘target’: ‘B’, ‘value’: 20},
     {‘source’: ‘A’, ‘target’: ‘C’, ‘value’: 10}]

     Convert the list to a dataframe for easier handling

     df = pd.DataFrame(data_list)

     Create a Sankey diagram

     sankey = go.Figure(data=[go.Sankey(
     node = dict(
     pad = 15,
     thickness = 20,
     line = dict(color = “black”, width = 0.5),
     label = [“Start”, “A”, “B”, “C”, “End”],
     color = [‘lightcoral’, ‘lightblue’, ‘lightcoral’, ‘lightblue’, ‘lightgrey’]
     ),
     link = dict(
     source = [0, 1, 1, 2, 3], # indices correspond to columns
     target = [1, 2, 3, 3, 4],
     value = [100, 100, 100, 100, 100]
     )
     ))])

     py.iplot(sankey, filename=’Sankey chart example’)

     “`

4. Customization and Final Touches: Once the chart is created, you can customize it further to make it more visually appealing and informative. This includes adding colors, adjusting arrow widths, and ensuring the labels are clear and concise.

Applications of Sankey Charts

Sankey diagrams are versatile and can be used in various fields and industries:

• Business and Economics: Showing investments and returns, or revenue and expenses over time.
• Energy and Sustainability: Illustrating energy flows in buildings or the lifecycle of products.
• Healthcare: Representing patient pathways through different health services or interventions.
• Political Analysis: Showing the flow of political contributions or the migration of voters between parties.
• Technology and Data Science: Visualizing data transformation pipelines, system architecture diagrams, or consumer interactions with web applications.

Conclusion

Sankey charts are a valuable tool for visualizing complex data flows and interconnections. By leveraging the power of visualization, they can help stakeholders understand processes, data, and systems more deeply. Whether you’re a data analyst, a researcher, or a business professional, Sankey diagrams are an excellent way to uncover insights and communicate findings in a clear, concise manner. Whether you’re analyzing energy efficiency, tracing data flows, or mapping political contributions, Sankey charts offer a unique way to understand the dynamics of complex systems.

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