javascript-d3How do I create a heatmap using JavaScript and D3?
Creating a heatmap using JavaScript and D3 is a fairly straightforward process.
First, you'll need to include the necessary libraries. This includes D3.js, as well as a color scale. For this example, we'll be using d3-scale-chromatic.
<script src="https://d3js.org/d3.v5.min.js"></script>
<script src="https://d3js.org/d3-scale-chromatic.v1.min.js"></script>
Next, you'll need to create the SVG element and set its width and height.
var svg = d3.select("body")
.append("svg")
.attr("width", 500)
.attr("height", 500);
After that, you'll need to create the color scale. This scale will be used to assign a color to each cell in the heatmap.
var colorScale = d3.scaleSequential(d3.interpolateReds)
.domain([1, 10]);
Then, you'll need to create the data array and draw the rectangles that will make up the heatmap.
var data = [
[1, 2, 3],
[4, 5, 6],
[7, 8, 9]
];
svg.selectAll("rect")
.data(data)
.enter()
.append("rect")
.attr("x", function(d, i) {
return i * 50;
})
.attr("y", function(d, i) {
return i * 50;
})
.attr("width", 50)
.attr("height", 50)
.style("fill", function(d) {
return colorScale(d);
});
Finally, you'll need to add some styling to make the heatmap look presentable.
svg.selectAll("rect")
.attr("stroke", "black")
.attr("stroke-width", 1);
The result should look something like this:
For more information, you can check out the d3-scale-chromatic and d3.js documentation.
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