Sankey charts, often heralded as the Swiss Army knife of data visualization professionals, offer a unique and powerful way to depict complex systems where materials, energy, or information move along a path, representing the dynamics of flow in a network. Their distinctive horizontal stream-like design makes it easier to decipher energy or substances that begin at one point and dissipate into another. Let’s explore the ins and outs of Sankey charts, from what they are and why they’re invaluable, to the methodological process of crafting them.
### Understanding Sankey Charts
At their heart, Sankey charts represent the flow of materials, energy, or other entities between different processes or locations in a process system. They are characterized by their thin, almost streamlike ‘streams,’ which thicken or thin according to the magnitude of flow being represented. The streams typically run from left to right, and there’s a clear emphasis on the magnitude and direction of flows.
Sankey diagrams are different from other types of flow charts, such as flowcharts or process maps, because they prioritize the quantity of material or energy being transferred. This means that Sankey charts can reveal inefficiencies and opportunities for improvement that may not be apparent in a more detailed process flow chart.
### The Evolution of Sankey Charts
Sankey diagrams were first created by Irish engineer, Mathematician, and economist William Playfair in the 1840s. They were initially used to report the energy efficiency of steam engines and have since been applied in numerous industries including mechanical and electrical systems, logistics, environmental science, business, and energy management.
### Key Features of Sankey Charts
– **Flow Proportional Width**: The width of the streams represents the proportion of the total flow. Thicker lines signify larger flows.
– **Consistent Flow Direction**: Sankey charts always flow consistently to the right, indicating the progress of a substance or energy from its source to its destination.
– **No Arrows or Nodes**: There are no arrows or nodes to denote direction or location changes within the streams.
– **Integration of Nodes**: Nodes can be integrated into the stream path itself if they represent an accumulation of flow.
– **Energy-Saving Representation**: Sankey diagrams effectively show where energy is lost or wasted, as these areas will typically have very thin streams.
### Creating a Sankey Chart
Creating a Sankey chart can be a nuanced endeavor but can be broken down into the following steps:
1. **Define the Flow**: Decide what material, energy, or information is flowing throughout your network.
2. **Outline Your Processes**: Map out the starting and ending points of the flow as well as the processes in between.
3. **Choose Your Sankey Chart Software**: You can create a Sankey chart using a variety of software tools such as Excel, PowerPoint, Gephi, or specialized Sankey chart software.
4. **Set the Parameters**: Determine how you will represent the flow and ensure the scaling is accurate.
5. **Start Drawing**: Begin laying down your streams, making sure they are proportionate to the flow being visualized.
6. **Annotate and Finalize**: Add labels and, if necessary, annotations to explain the flow and any points of interest.
### Benefits of Sankey Diagrams
Sankey charts are particularly effective for several reasons:
– **Highlighting Energy Waste**: They quickly identify areas where energy, money, or material is lost.
– **Comparative Analysis**: Sankey diagrams are great for comparing different flows between similar systems.
– **Educational Tool**: They communicate complex information easily, making them ideal for educational purposes.
– **Insight into Large-Scale Systems**: They help to illustrate the energy or material flow in a large-scale system, such as across cities, countries, or across organizational departments.
As data visualization continues to play an increasingly significant role in decision-making, Sankey charts stand out as a powerful, specialized tool for decoding the flow within complex systems. Whether analyzing the energy efficiency of a building, tracking the logistics of an industrial process, or mapping the financial flows of a business, the Sankey chart is truly a versatile ally to have in your data visualization arsenal.
