D3 Scatter Plot

So far, we’ve drawn only bar charts with simple data — just one-dimensional sets of numbers. But when you have two sets of values to plot against each other, you need a second dimension.

What is scatter plot?

The scatter plot is a common type of visualization that represents two sets of corresponding values on two different axis: horizontal and vertical, x and y. As per Wikipedia we can say A scatter plot, scatter plot, or scatter graph is a type of mathematical diagram using Cartesian coordinates to display values for two variables for a set of data.

The Data:

As you saw in Types of data, you have a lot of flexibility around how you structure your data set. For our scatter plot, we will have a tsv data set. Which we need to import. You can use any kind of data you want as a tsv file. To import the data, we will follow the code structure as we have done in other chart examples.

d3.tsv("data.tsv", function(error, data) {
data.forEach(function(d) {
d.Length = +d.Length;
d.Width = +d.Width;
});

The scatter plot:

Let’s carry over most of the code from our bar chart experiments, including the piece that creates the SVG element:

var svg = d3.select("body").append("svg")
.attr("width", width + margin.left + margin.right)
.attr("height", height + margin.top + margin.bottom)
.append("g")
.attr("transform", "translate(" + margin.left + "," + margin.top + ")");

Instead of creating rects, however, we’ll make a circle for each data point:

 svg.selectAll(".dot")
.data(data)
.enter().append("circle")
.attr("class", "dot")
.attr("r", 10)
.attr("cx", function(d) { return x(d.Width); })
.attr("cy", function(d) { return y(d.Length); })
.style("fill", function(d) { return color(d.species); });

Now as we have done all the important things, let us see the complete code and what it looks like.

<!DOCTYPE html>
<meta charset="utf-8">
<style>
body {
font: 10px sans-serif;
}
.axis path,
.axis line {
fill: none;
stroke: #000;
shape-rendering: crispEdges;
}
.dot {
stroke: #000;
}
</style>
<body>
<script src="http://d3js.org/d3.v3.min.js"></script>
<script>
var margin = {top: 20, right: 20, bottom: 30, left: 40},
width = 960 - margin.left - margin.right,
height = 500 - margin.top - margin.bottom;
var x = d3.scale.linear()
.range([0, width]);
var y = d3.scale.linear()
.range([height, 0]);
var color = d3.scale.category10();
var xAxis = d3.svg.axis()
.scale(x)
.orient("bottom");
var yAxis = d3.svg.axis()
.scale(y)
.orient("left");
var svg = d3.select("body").append("svg")
.attr("width", width + margin.left + margin.right)
.attr("height", height + margin.top + margin.bottom)
.append("g")
.attr("transform", "translate(" + margin.left + "," + margin.top + ")");
d3.tsv("data.tsv", function(error, data) {
data.forEach(function(d) {
d.Length = +d.Length;
d.Width = +d.Width;
});
x.domain(d3.extent(data, function(d) { return d.Width; })).nice();
y.domain(d3.extent(data, function(d) { return d.Length; })).nice();
svg.append("g")
.attr("class", "x axis")
.attr("transform", "translate(0," + height + ")")
.call(xAxis)
.append("text")
.attr("class", "label")
.attr("x", width)
.attr("y", -6)
.style("text-anchor", "end")
.text("Width (m)");
svg.append("g")
.attr("class", "y axis")
.call(yAxis)
.append("text")
.attr("class", "label")
.attr("transform", "rotate(-90)")
.attr("y", 6)
.attr("dy", ".71em")
.style("text-anchor", "end")
.text("Length (km)")
svg.selectAll(".dot")
.data(data)
.enter().append("circle")
.attr("class", "dot")
.attr("r", 10)
.attr("cx", function(d) { return x(d.Width); })
.attr("cy", function(d) { return y(d.Length); })
.style("fill", function(d) { return color(d.species); });
var legend = svg.selectAll(".legend")
.data(color.domain())
.enter().append("g")
.attr("class", "legend")
.attr("transform", function(d, i) { return "translate(0," + i * 20 + ")"; });
legend.append("rect")
.attr("x", width - 18)
.attr("width", 18)
.attr("height", 18)
.style("fill", color);
legend.append("text")
.attr("x", width - 24)
.attr("y", 9)
.attr("dy", ".35em")
.style("text-anchor", "end")
.text(function(d) { return d; });

});
</script>
</body>
</html>

Below we can see the output of the example above.

scatterplot

Though it is a basic example of scatter plot we can add other modifications to it.

If you find this article helpful, you can connect us in <strong><a href=”https://plus.google.com/u/0/b/101884616246631821987/” target=”_blank” rel=”nofollow”>Google+</a></strong> and<strong> <a href=”https://twitter.com/phloxblog” target=”_blank” rel=”nofollow”>Twitter</a></strong>.

1 thought on “D3 Scatter Plot

Leave a Reply

Your email address will not be published. Required fields are marked *