Flowing Ideas: Uncovering Data Stories with Sankey Charts

Sankey diagrams, a variant of flowcharts, have become a powerful tool for visualizing complex data flows and are especially useful in data analysis, environmental sciences, and any scenario involving the flow of material or information. This article delves into the creation of sankey charts, highlighting their applications and offering insights into how they can help uncover the stories hidden within your data.

Understanding Sankey Charts

A sankey chart is a graphical representation of data flow through a system, showcasing how the amount of something changes from one category to another. These diagrams are particularly useful for understanding the flow of information, financial data, or any kind of material over time or between systems. The structure is composed of blocks or nodes linked by arrows or streams that vary in width, proportional to the quantity being represented.

Key Components of a Sankey Chart

1. Nodes: Represent the starting points and ending points of the flow. In the context of data, these could be input data points or categories.

2. Flows: The connected lines or streams represent the actual flow. The width of the stream corresponds to the quantity or volume of the flow.

3. Sources and Destinations: The points from which the flow originates and into which the flow ends, respectively.

4. Scales: Metrics along the vertical axis indicating the quantity represented by the flow.

Creating a Sankey Chart

Creating a sankey chart can be done manually, though it’s often more convenient to use software or programming languages designed to generate them. Here’s a basic overview of creating a sankey chart using R, a popular programming language for statistical computing and graphics:

1. Prepare Your Dataset: Ensure your data is in a tidy format. This means that each row represents a flow, and each column represents a category or flow step.

2. Select a Sankey Plot Library: R offers several libraries for creating sankey diagrams, including ggplot2 and networkD3. For this example, we’ll use ggplot2 with the direct_aes package.

   R
library(ggplot2)
library(direct_aes)


3. Format Your Data: Your data should look something like this:

   
Source, Destination, Amount
A, B, 100
A, C, 200
B, D, 50
C, E, 150


   You can then calculate the cumulative amount per step if you want to align the flows.

4. Apply the Data to the Chart:

   R
ggplot(data, aes(x = Step, y = Cumulative, width = Width, height = 0.1, label = Amount)) +
geom_direct_aes(direction = 'h') +
geom_richtext(aes(x = Start, y = 0, label = Start, vjust = 1), data = data, stat = "桑葉", check_overlap = TRUE) +
geom_richtext(aes(x = End, y = 0, label = End, vjust = -1), data = data, stat = "桑葉", check_overlap = TRUE) +
scale_x_continuous(breaks = seq_len(nrow(data)), labels = function(x) names(data)[x]) +
theme_minimal()


Applications of Sankey Charts

Sankey charts are applicable in various fields and contexts. Here are some notable examples:

• Financial Analysis: Visualizing the flow of financial transactions between accounts, projects, or other entities.
• Energy Flow: Representing the efficiency of energy flows within buildings, plants, or entire cities.
• Data Processes: Explaining the journey of information through data collection, processing, and analysis phases.
• Resource Management: Tracking the flow of materials through supply chains.

Conclusion

Sankey charts are an effective method for visualizing and analyzing complex data flows, making them an invaluable tool in modern data storytelling. By highlighting the nuances within your data, sankey charts offer a clear and concise way to understand complex processes. Whether you’re analyzing energy consumption, tracking financial transactions, or mapping the evolution of trends over time, Sankey diagrams provide a powerful method to reveal the stories hidden in your data.

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.