Using d3-brush to zoom to the brushed region. Double-click or double-tap to zoom out. Another approach is to use Focus + Context.
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June 16, 2020 16:28
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Brush & Zoom II
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| license: gpl-3.0 | |
| height: 600 |
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| <!DOCTYPE html> | |
| <meta charset="utf-8"> | |
| <svg width="960" height="600"></svg> | |
| <script src="//d3js.org/d3.v4.min.js"></script> | |
| <script> | |
| var random = d3.randomNormal(0, 0.2), | |
| sqrt3 = Math.sqrt(3), | |
| points0 = d3.range(300).map(function() { return [random() + sqrt3, random() + 1, 0]; }), | |
| points1 = d3.range(300).map(function() { return [random() - sqrt3, random() + 1, 1]; }), | |
| points2 = d3.range(300).map(function() { return [random(), random() - 1, 2]; }), | |
| points = d3.merge([points0, points1, points2]); | |
| var svg = d3.select("svg"), | |
| width = +svg.attr("width"), | |
| height = +svg.attr("height"); | |
| var k = height / width, | |
| x0 = [-4.5, 4.5], | |
| y0 = [-4.5 * k, 4.5 * k], | |
| x = d3.scaleLinear().domain(x0).range([0, width]), | |
| y = d3.scaleLinear().domain(y0).range([height, 0]), | |
| z = d3.scaleOrdinal(d3.schemeCategory10); | |
| var xAxis = d3.axisTop(x).ticks(12), | |
| yAxis = d3.axisRight(y).ticks(12 * height / width); | |
| var brush = d3.brush().on("end", brushended), | |
| idleTimeout, | |
| idleDelay = 350; | |
| svg.selectAll("circle") | |
| .data(points) | |
| .enter().append("circle") | |
| .attr("cx", function(d) { return x(d[0]); }) | |
| .attr("cy", function(d) { return y(d[1]); }) | |
| .attr("r", 2.5) | |
| .attr("fill", function(d) { return z(d[2]); }); | |
| svg.append("g") | |
| .attr("class", "axis axis--x") | |
| .attr("transform", "translate(0," + (height - 10) + ")") | |
| .call(xAxis); | |
| svg.append("g") | |
| .attr("class", "axis axis--y") | |
| .attr("transform", "translate(10,0)") | |
| .call(yAxis); | |
| svg.selectAll(".domain") | |
| .style("display", "none"); | |
| svg.append("g") | |
| .attr("class", "brush") | |
| .call(brush); | |
| function brushended() { | |
| var s = d3.event.selection; | |
| if (!s) { | |
| if (!idleTimeout) return idleTimeout = setTimeout(idled, idleDelay); | |
| x.domain(x0); | |
| y.domain(y0); | |
| } else { | |
| x.domain([s[0][0], s[1][0]].map(x.invert, x)); | |
| y.domain([s[1][1], s[0][1]].map(y.invert, y)); | |
| svg.select(".brush").call(brush.move, null); | |
| } | |
| zoom(); | |
| } | |
| function idled() { | |
| idleTimeout = null; | |
| } | |
| function zoom() { | |
| var t = svg.transition().duration(750); | |
| svg.select(".axis--x").transition(t).call(xAxis); | |
| svg.select(".axis--y").transition(t).call(yAxis); | |
| svg.selectAll("circle").transition(t) | |
| .attr("cx", function(d) { return x(d[0]); }) | |
| .attr("cy", function(d) { return y(d[1]); }); | |
| } | |
| </script> |
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Akshay, the reason for the timeout is to capture double click events. Mouse-up on the graph triggers a brush end. The first time this happens, we set the timer to clear
idleTimeout, which tracks whether we've recently (at mostidleDelayms ago) clicked. The second time we mouse-up, one of two things can happen: either the timer has expired, in which caseidleTimeoutisnullagain and so we return without changing things; or the timer hasn't expired, in which caseidleTimeoutis notnulland we continue on to setx.domainandy.domain.In other words the timer is there to make sure we've double clicked and not just single clicked.