Tree graphs are an excellent way to visualize hierarchical data, showing the tree structure of the data and the relationships between the nodes. In D3, there are several ways to create tree visualizations, such as expansion trees, dendrograms, and circular trees. In this chapter, we will learn to create basic tree graphs using D3.

Sample Data

For this chapter, we will use a sample hierarchical data set:

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SVG Setup

First, we set up the SVG area where the tree graph will be drawn:

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Creating the Tree Structure

We use D3's tree layout to establish the positions of the tree's nodes and links:

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Creating Links

We draw the link lines between parent and child nodes:

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Creating Nodes

We draw the tree nodes:

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Styling Customization

We can add CSS styles to enhance the appearance of the tree graph:

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Interactivity

We will add basic interactivity, such as expanding/collapsing nodes on click:

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Summary

In this chapter, we learned to create a tree graph in D3. We started with the basic setup of the drawing area and then created the tree structure using D3's tree layout. We drew the tree's links and nodes and added interactivity to expand and collapse nodes.

Tree graphs are a powerful tool for visualizing hierarchical data structures, and you now have the tools to create and customize your tree graphs using D3.

In the next chapter, we will explore how to create pie and donut charts.