Sankey diagrams are a powerful tool for visualizing flows and connections in data. They are named after Captain Matthew Henry Phineas Riall Sankey, who developed the first such diagram in 1898 to illustrate the energy flow in a steam engine. Since then, Sankey diagrams have become popular in a variety of fields, including physics, economics, and energy management, for their ability to clearly show the direction and magnitude of data flows.
In this article, we will explore how to create and apply Sankey diagrams in your work, focusing on the benefits they offer and how to make them visually appealing.
Creating a Sankey Diagram

Sankey diagrams display flows and connections in a visually engaging and informative way, making them a popular choice for data visualization. The key elements of a Sankey diagram are:

• Nodes: These represent the starting and ending points of flows.
• Connections: These are lines that connect the nodes, and they are color-coded to indicate the magnitude or type of flow.
• Flow Labels: These provide additional information about the flows between the nodes, such as the quantity or percentage of data.

To create a Sankey diagram, you’ll need data that includes the following information:

• Source nodes: The starting points of each flow.
• Sink nodes: The ending points of each flow.
• Flows between nodes: The quantity or type of flow between the nodes.

There are many software tools available for creating Sankey diagrams, including Excel, Tableau, R, and Python libraries. In this article, we will use Python and the Plotly library, which provides an easy-to-use interface for creating dynamic Sankey diagrams.

First, we’ll need to install Plotly and its Python dependencies by running the following commands:


pip install plotly
pip install pandas


Once we’ve installed the necessary libraries, we can use the following code to create a simple Sankey diagram:

“`python
import plotly.graph_objects as go

Define the data

nodes = [‘A’, ‘B’, ‘C’]
link = [
{‘source’: 0, ‘target’: 1, ‘value’: 6},
{‘source’: 1, ‘target’: 2, ‘value’: 3},
{‘source’: 0, ‘target’: 2, ‘value’: 2}
]
node_attrs = {‘pad’: 10, ‘thickness’: 10, ‘color’: ‘lightgray’, ‘font’: {‘color’: ‘black’, ‘size’: 12}}

Create the diagram

fig = go.Figure(data=[go.Sankey(
node = dict(
pad = 15,
thickness = 20,
line = dict(color = “black”, width = 0.5),
label = nodes,
color = “red”
),
link = dict(
source = [link[i][‘source’] for i in range(len(link))],
target = [link[i][‘target’] for i in range(len(link))],
value = [link[i][‘value’] for i in range(len(link))]
)
)])
fig.updatelayout(titletext=”Simple Sankey Diagram”, font_size=10)
fig.show()
“`

This code creates a simple Sankey diagram with three nodes and three flows between them. The node dictionary specifies the layout and appearance of the nodes, while the link dictionary specifies the connections and quantities of flow between the nodes.

Applications of Sankey Diagrams

Sankey diagrams can be used in a variety of fields to visualize complex data flows, such as material or energy flows in physical systems, economic flows in financial systems, and data flows in information systems. Here are some examples of how Sankey diagrams can be applied:

• Energy Flow Diagrams: Sankey diagrams can illustrate the flow of energy in various systems, such as power systems, buildings, and transportation systems. They can show the sources of energy, the energy conversion processes, and the ultimate destinies of the energy, such as consumption or waste.

• Supply Chain Diagrams: Sankey diagrams can visualize the flows in a supply chain, such as the movement of goods and materials, or the flow of information between supply chain actors. They can show the distribution channels, the inventory levels, and the demand patterns.

• Network Diagrams: Sankey diagrams can visualize the flows between network nodes, such as the traffic flow in transportation networks, or the data flow in communication networks. They can show the network topology, the traffic patterns, and the latency or delay in the network.

Conclusion

Sankey diagrams are a powerful tool for visualizing complex data flows and connections. They can improve understanding, communication, and decision-making in a wide range of fields. By following the steps outlined in this article and using the Plotly library, you can create appealing and informative Sankey diagrams that engage your audience and convey your message effectively.

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