This is document gives a few insights on how to add a zooming feature with d3.js. It is composed by several interactive examples, allowing to play with the code to understand better how it works.
d3.zoom()<!DOCTYPE html>
<meta charset="utf-8">
<!-- Load d3.js -->
<script src="https://d3js.org/d3.v4.js"></script>
<!-- Create a div where the circle will take place -->
<div id="dataviz_basicZoom"></div>
<script>
// append the svg object to the body of the page
var svg = d3.select("#dataviz_basicZoom")
.append("svg")
.attr("width", 460)
.attr("height", 460)
.call(d3.zoom().on("zoom", function () {
svg.attr("transform", d3.event.transform)
}))
.append("g")
svg
.append("circle")
.attr("cx", 300)
.attr("cy", 300)
.attr("r", 40)
.style("fill", "#68b2a1")
</script> <!DOCTYPE html>
<meta charset="utf-8">
<!-- Load d3.js -->
<script src="https://d3js.org/d3.v4.js"></script>
<!-- Create a div where the circle will take place -->
<div id="dataviz_axisZoom"></div>
<script>
// set the dimensions and margins of the graph
var margin = {top: 10, right: 30, bottom: 30, left: 60},
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("#dataviz_axisZoom")
.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 + ")");
//Read the data
d3.csv("https://raw.githubusercontent.com/holtzy/D3-graph-gallery/master/DATA/iris.csv", function(data) {
// Add X axis
var x = d3.scaleLinear()
.domain([4, 8])
.range([ 0, width ]);
var xAxis = SVG.append("g")
.attr("transform", "translate(0," + height + ")")
.call(d3.axisBottom(x));
// Add Y axis
var y = d3.scaleLinear()
.domain([0, 9])
.range([ height, 0]);
var yAxis = SVG.append("g")
.call(d3.axisLeft(y));
// Add a clipPath: everything out of this area won't be drawn.
var clip = SVG.append("defs").append("SVG:clipPath")
.attr("id", "clip")
.append("SVG:rect")
.attr("width", width )
.attr("height", height )
.attr("x", 0)
.attr("y", 0);
// Create the scatter variable: where both the circles and the brush take place
var scatter = SVG.append('g')
.attr("clip-path", "url(#clip)")
// Add circles
scatter
.selectAll("circle")
.data(data)
.enter()
.append("circle")
.attr("cx", function (d) { return x(d.Sepal_Length); } )
.attr("cy", function (d) { return y(d.Petal_Length); } )
.attr("r", 8)
.style("fill", "#61a3a9")
.style("opacity", 0.5)
// Set the zoom and Pan features: how much you can zoom, on which part, and what to do when there is a zoom
var zoom = d3.zoom()
.scaleExtent([.5, 20]) // This control how much you can unzoom (x0.5) and zoom (x20)
.extent([[0, 0], [width, height]])
.on("zoom", updateChart);
// This add an invisible rect on top of the chart area. This rect can recover pointer events: necessary to understand when the user zoom
SVG.append("rect")
.attr("width", width)
.attr("height", height)
.style("fill", "none")
.style("pointer-events", "all")
.attr('transform', 'translate(' + margin.left + ',' + margin.top + ')')
.call(zoom);
// now the user can zoom and it will trigger the function called updateChart
// A function that updates the chart when the user zoom and thus new boundaries are available
function updateChart() {
// recover the new scale
var newX = d3.event.transform.rescaleX(x);
var newY = d3.event.transform.rescaleY(y);
// update axes with these new boundaries
xAxis.call(d3.axisBottom(newX))
yAxis.call(d3.axisLeft(newY))
// update circle position
scatter
.selectAll("circle")
.attr('cx', function(d) {return newX(d.Sepal_Length)})
.attr('cy', function(d) {return newY(d.Petal_Length)});
}
})
</script> clipPath is used to avoid displaying the
circle outside the chart area.
all(brush.move, null) is used to dismiss the
grey brushing area once the selection has been done.
<!DOCTYPE html>
<meta charset="utf-8">
<!-- Load d3.js -->
<script src="https://d3js.org/d3.v4.js"></script>
<!-- Create a div where the circle will take place -->
<div id="dataviz_brushZoom"></div>
<script>
// set the dimensions and margins of the graph
var margin = {top: 10, right: 30, bottom: 30, left: 60},
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("#dataviz_brushZoom")
.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 + ")");
//Read the data
d3.csv("https://raw.githubusercontent.com/holtzy/D3-graph-gallery/master/DATA/iris.csv", function(data) {
// Add X axis
var x = d3.scaleLinear()
.domain([4, 8])
.range([ 0, width ]);
var xAxis = Svg.append("g")
.attr("transform", "translate(0," + height + ")")
.call(d3.axisBottom(x));
// Add Y axis
var y = d3.scaleLinear()
.domain([0, 9])
.range([ height, 0]);
Svg.append("g")
.call(d3.axisLeft(y));
// Add a clipPath: everything out of this area won't be drawn.
var clip = Svg.append("defs").append("svg:clipPath")
.attr("id", "clip")
.append("svg:rect")
.attr("width", width )
.attr("height", height )
.attr("x", 0)
.attr("y", 0);
// Color scale: give me a specie name, I return a color
var color = d3.scaleOrdinal()
.domain(["setosa", "versicolor", "virginica" ])
.range([ "#440154ff", "#21908dff", "#fde725ff"])
// Add brushing
var brush = d3.brushX() // Add the brush feature using the d3.brush function
.extent( [ [0,0], [width,height] ] ) // initialise the brush area: start at 0,0 and finishes at width,height: it means I select the whole graph area
.on("end", updateChart) // Each time the brush selection changes, trigger the 'updateChart' function
// Create the scatter variable: where both the circles and the brush take place
var scatter = Svg.append('g')
.attr("clip-path", "url(#clip)")
// Add circles
scatter
.selectAll("circle")
.data(data)
.enter()
.append("circle")
.attr("cx", function (d) { return x(d.Sepal_Length); } )
.attr("cy", function (d) { return y(d.Petal_Length); } )
.attr("r", 8)
.style("fill", function (d) { return color(d.Species) } )
.style("opacity", 0.5)
// Add the brushing
scatter
.append("g")
.attr("class", "brush")
.call(brush);
// A function that set idleTimeOut to null
var idleTimeout
function idled() { idleTimeout = null; }
// A function that update the chart for given boundaries
function updateChart() {
extent = d3.event.selection
// If no selection, back to initial coordinate. Otherwise, update X axis domain
if(!extent){
if (!idleTimeout) return idleTimeout = setTimeout(idled, 350); // This allows to wait a little bit
x.domain([ 4,8])
}else{
x.domain([ x.invert(extent[0]), x.invert(extent[1]) ])
scatter.select(".brush").call(brush.move, null) // This remove the grey brush area as soon as the selection has been done
}
// Update axis and circle position
xAxis.transition().duration(1000).call(d3.axisBottom(x))
scatter
.selectAll("circle")
.transition().duration(1000)
.attr("cx", function (d) { return x(d.Sepal_Length); } )
.attr("cy", function (d) { return y(d.Petal_Length); } )
}
})
</script>