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D3 Tips and Tricks: Interactive Data Visualization

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Explore how to implement interactive tooltips in D3 scatter plots by combining CSS styling and JavaScript event handling. Understand how to configure tooltip appearance, format data display, and manage mouse events to create smooth fade-in and fade-out transitions. This lesson helps you enhance user interaction by dynamically displaying relevant data points as users hover over chart elements.

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So, bolstered with a couple of new concepts to consider, let’s see how they are enacted in practice.

If we start with our simple-scatter plot graph, there are four areas in it that we will want to modify.

CSS

The first area is the CSS. The following code should be added just before the </style> tag:

div.tooltip {
  position: absolute;
  text-align: center;
  width: 60px;
  height: 28px;
  padding: 2px;
  font: 12px sans-serif;
  background: lightsteelblue;
  border: 0px;
  border-radius: 8px;
  pointer-events: none;
}

  • These styles are defining how our tooltip will appear. Most of them are fairly straight forward. The position of the tooltip is done in absolute measurements and not relative. The text is center-aligned, and the height, width, and color of the rectangle is 28px, 60px, and lightsteelblue, respectively. The “padding” is an interesting feature that provides a neat way to grow a shape by a fixed amount from a specified size.

  • We set the border to 0px so that it doesn’t show up, and a neat style (attribute?) called border-radius provides the nice rounded corners on the rectangle.

  • Lastly, but by no means least, the pointer-events: none line ...