Line charts are useful for visualizing continuous data over time, showing trends and changes. In this chapter, we'll learn how to create line charts using D3. We'll see how to bind data, set up scales and axes, and plot lines on an SVG.

Sample Data

For this chapter, we'll use a sample dataset representing measurements on different days:

javascript

Setting up the SVG

First, we'll set up the SVG area where the line chart will be drawn:

javascript

Scales

We need scales for the X and Y axes.

X Scale

We use a time scale for the X axis:

javascript

Y Scale

For the Y axis, we use a linear scale:

javascript

Axes

We create and add the X and Y axes using the defined scales:

javascript

Creating the Line

D3 provides a line generator function that makes it easy to draw lines based on data:

javascript

Customizing the Line Chart

We can customize the line chart to make it more visually appealing. For example, by adding points at the line intersections:

javascript

And we can add CSS styles to improve its appearance:

style.css

css

Interactivity

Let's add basic interactivity, such as a tooltip that shows the value when hovering over a point:

javascript

Summary

In this chapter, we learned how to create a line chart in D3. We started with the basic setup of the drawing area and then created the scales and axes. We plotted the line using the line generator function and added points for better visibility. Finally, we added basic interactivity with tooltips.

Line charts are fundamental for showing continuous data and trends over time. Now you have the tools to create and customize your own line charts using D3.

In the next chapter, we will explore how to create area charts, which are a natural extension of line charts.