This post describes how to build a
histogram
with d3.js and add a slider that controls bin size. It is important to
play with bin size since the conclusion can become
significantly different.
This example works with d3.js v4 and v6
div that will be modified by d3 later on.
svg area. It specify the chart size and its
margin. Read more.
d3.histogram() function that will compute the
binning and returns the coordinates of each bar.
.append("rect") approach.
<!DOCTYPE html>
<meta charset="utf-8">
<!-- Load d3.js -->
<script src="https://d3js.org/d3.v4.js"></script>
<!-- Create a div where the graph will take place -->
<div id="my_dataviz"></div>
<p>
<label># bins</label>
<input type="number" min="1" max="100" step="30" value="20" id="nBin">
</p>
<!DOCTYPE html>
<meta charset="utf-8">
<!-- Load d3.js -->
<script src="https://d3js.org/d3.v6.js"></script>
<!-- Create a div where the graph will take place -->
<div id="my_dataviz"></div>
<p>
<label># bins</label>
<input type="number" min="1" max="100" step="30" value="20" id="nBin">
</p>
<script>
// set the dimensions and margins of the graph
var margin = {top: 10, right: 30, bottom: 30, left: 40},
width = 460 - margin.left - margin.right,
height = 400 - margin.top - margin.bottom;
// append the svg object to the body of the page
var svg = d3.select("#my_dataviz")
.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 + ")");
// get the data
d3.csv("https://raw.githubusercontent.com/holtzy/data_to_viz/master/Example_dataset/1_OneNum.csv", function(data) {
// X axis: scale and draw:
var x = d3.scaleLinear()
.domain([0, 1000]) // can use this instead of 1000 to have the max of data: d3.max(data, function(d) { return +d.price })
.range([0, width]);
svg.append("g")
.attr("transform", "translate(0," + height + ")")
.call(d3.axisBottom(x));
// Y axis: initialization
var y = d3.scaleLinear()
.range([height, 0]);
var yAxis = svg.append("g")
// A function that builds the graph for a specific value of bin
function update(nBin) {
// set the parameters for the histogram
var histogram = d3.histogram()
.value(function(d) { return d.price; }) // I need to give the vector of value
.domain(x.domain()) // then the domain of the graphic
.thresholds(x.ticks(nBin)); // then the numbers of bins
// And apply this function to data to get the bins
var bins = histogram(data);
// Y axis: update now that we know the domain
y.domain([0, d3.max(bins, function(d) { return d.length; })]); // d3.hist has to be called before the Y axis obviously
yAxis
.transition()
.duration(1000)
.call(d3.axisLeft(y));
// Join the rect with the bins data
var u = svg.selectAll("rect")
.data(bins)
// Manage the existing bars and eventually the new ones:
u
.enter()
.append("rect") // Add a new rect for each new elements
.merge(u) // get the already existing elements as well
.transition() // and apply changes to all of them
.duration(1000)
.attr("x", 1)
.attr("transform", function(d) { return "translate(" + x(d.x0) + "," + y(d.length) + ")"; })
.attr("width", function(d) { return x(d.x1) - x(d.x0) -1 ; })
.attr("height", function(d) { return height - y(d.length); })
.style("fill", "#69b3a2")
// If less bar in the new histogram, I delete the ones not in use anymore
u
.exit()
.remove()
}
// Initialize with 20 bins
update(20)
// Listen to the button -> update if user change it
d3.select("#nBin").on("input", function() {
update(+this.value);
});
});
</script> <script>
// set the dimensions and margins of the graph
const margin = {top: 10, right: 30, bottom: 30, left: 40},
width = 460 - margin.left - margin.right,
height = 400 - margin.top - margin.bottom;
// append the svg object to the body of the page
const svg = d3.select("#my_dataviz")
.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})`);
// get the data
d3.csv("https://raw.githubusercontent.com/holtzy/data_to_viz/master/Example_dataset/1_OneNum.csv").then( function(data) {
// X axis: scale and draw:
const x = d3.scaleLinear()
.domain([0, 1000]) // can use this instead of 1000 to have the max of data: d3.max(data, function(d) { return +d.price })
.range([0, width]);
svg.append("g")
.attr("transform", `translate(0,${height})`)
.call(d3.axisBottom(x));
// Y axis: initialization
const y = d3.scaleLinear()
.range([height, 0]);
const yAxis = svg.append("g")
// A function that builds the graph for a specific value of bin
function update(nBin) {
// set the parameters for the histogram
const histogram = d3.histogram()
.value(function(d) { return d.price; }) // I need to give the vector of value
.domain(x.domain()) // then the domain of the graphic
.thresholds(x.ticks(nBin)); // then the numbers of bins
// And apply this function to data to get the bins
const bins = histogram(data);
// Y axis: update now that we know the domain
y.domain([0, d3.max(bins, function(d) { return d.length; })]); // d3.hist has to be called before the Y axis obviously
yAxis
.transition()
.duration(1000)
.call(d3.axisLeft(y));
// Join the rect with the bins data
const u = svg.selectAll("rect")
.data(bins)
// Manage the existing bars and eventually the new ones:
u
.join("rect") // Add a new rect for each new elements
.transition() // and apply changes to all of them
.duration(1000)
.attr("x", 1)
.attr("transform", function(d) { return `translate(${x(d.x0)}, ${y(d.length)})`})
.attr("width", function(d) { return x(d.x1) - x(d.x0) -1 ; })
.attr("height", function(d) { return height - y(d.length); })
.style("fill", "#69b3a2")
}
// Initialize with 20 bins
update(20)
// Listen to the button -> update if user change it
d3.select("#nBin").on("input", function() {
update(+this.value);
});
});
</script>