Sankey charts are a unique and highly effective way to visualize the flow of information, resources, or energy. These flow diagrams are especially valuable in illustrating complex processes where the direction and magnitude of flows are important. But what exactly makes a Sankey chart stand out and how do you make one that tells a compelling story? Let’s dive deep into the world of Sankey charts with our comprehensive guide to creating these impressive visualizations.
### What is a Sankey Chart?
Sankey charts provide a visual representation of material, energy, or cost flows within an industrial system or complex system processes. They are named after English engineer and physicist William Playfair who was first to use such diagrams in 1848 to analyze and report energy conversions.
Their distinctive feature is the thickness of arrows which represents the quantity of flow. Thicker lines signify higher flow quantities, while the thinner lines represent lesser amounts. This design communicates the scale of each flow at a glance, making an otherwise complex data set far more digestible.
### The Components of a Sankey Chart
Before you begin crafting your own Sankey chart, familiarize yourself with its key components:
– **Nodes**: These are the points of entry and exit of flows in the system. In a Sankey chart, they’re typically represented as dots or shapes.
– **Arrows**: Arrows depict flows between nodes. Their width varies according to the magnitude of the flow.
– **Axes**: These are used to scale the flow values. If the data set is large, you might consider log scales.
– **Labels**: Include clear, concise labels for the nodes and flows to make the chart intuitive.
### Creating a Sankey Chart: How-to
**Step 1: Identify and Gather Data**
Begin by collecting the data that will populate your Sankey chart. You’ll typically need information about the quantities and flows, both at a high-level and at the node level.
**Step 2: Choose Diagram Layout**
Determine the diagram layout by deciding where to place your nodes and how to depict the flows. The layout is crucial for keeping the chart clear and readable.
**Step 3: Determine Flow Widths**
For each flow, calculate the width of the arrow. This can be done using a simple formula that takes the flow size and scales it according to the chosen axis scale.
**Step 4: Assign Nodes to Flows**
Nodes should be assigned to represent the inputs and outputs of the system you are visualizing. This step will determine the connectivity of your flows.
**Step 5: Assemble the Diagram**
Start placing nodes and arrows using your chosen software or manual drawing methods. Ensure that the thickness of the lines corresponds to the actual flow sizes.
**Step 6: Review and Refine**
It’s critical to review your Sankey chart for accuracy. Adjust the flow widths, check the placement of nodes, and ensure the axes are scaled appropriately. Look for ways to simplify the chart without losing critical information.
### Best Practices for Sankey Charts
– **Be Clear**: Ensure that your chart is easy to understand at first glance.
– **Prioritize**: Emphasize the larger flows by making them thicker; this will help the audience focus on the most substantial data.
– **Be Economical**: Avoid clutter by carefully considering what should and should not be shown.
– **Minimize Intrusions**: Keep annotations to the minimum and allow the flow arrows to take precedent.
– **Consistency**: The Sankey chart’s axes should be scaled consistently across the whole chart, making comparisons easier.
### Tools for Creating Sankey Charts
Several software tools can help you create Sankey charts. A few popular ones include:
– **Tableau**: Known for its data visualization capabilities, Tableau offers a Sankey chart option.
– **Microsoft Excel**: With the right add-ons or formulas, Sankey charts can be created within Excel.
– **Gephi**: A powerful, open-source graph analysis and visualization software that can create detailed Sankey diagrams.
– **Sankey Diagrams**: This is a JavaScript library specifically designed to draw Sankey diagrams in HTML5.
Creating an effective Sankey chart requires patience and attention to detail. But with a clear understanding of the process and the right tools, you can produce compelling visualizations that elucidate the essence of complex data and systems. Now equipped with our guide, you should be well on your way to crafting informative, impactful Sankey charts.
