I am using Mike Bostok's Block for brushing a scatterplot matrix.
I want to brush the diagonal plots of the matrix using an opacity number; middle of brush range opacity = 1 and opacity value = low on the sides of the brush range.
I couldn't find a hint online, besides this question, which does an identical action but using dc.js (with help of pretransition attribute).
Can this be achieved in d3?
1 Answers
Answers 1
Interesting question.
Here's a code snippet that'll set opacity on the selected circles by their distance from the center of the selection. It does this on the brush end with a nice transition. Here's the relevant method:
function brushend(p) { // reset opacity svg.selectAll("circle").style('opacity', 1); // if no brush then bail if (brush.empty()) { svg.selectAll(".hidden").classed("hidden", false); return; } // some calculations var e = brush.extent(), xC = (e[1][0] + e[0][0]) / 2, yC = (e[1][1] + e[0][1]) / 2, // maxD is the maximum of the distance to the two edges maxD = Math.max( Math.sqrt((xC - e[0][0])**2), Math.sqrt ((yC - e[0][1])**2) ); // those circles not hidden svg.selectAll("circle:not(.hidden)") .transition() .duration(1000) .style("opacity", function(d) { // distance from furthest edge var xD = Math.sqrt( (xC - d[p.x])**2 + (yC - d[p.y])**2 ); // set opacity as percent of distance return (maxD - xD) / maxD; }); } Running Code:
<!DOCTYPE html> <meta charset="utf-8"> <style> svg { font: 10px sans-serif; padding: 10px; } .axis, .frame { shape-rendering: crispEdges; } .axis line { stroke: #ddd; } .axis path { display: none; } .cell text { font-weight: bold; text-transform: capitalize; } .frame { fill: none; stroke: #aaa; } circle { fill-opacity: .7; } circle.hidden { fill: #ccc !important; } .extent { fill: #000; fill-opacity: .125; stroke: #fff; } </style> <body> <script src="//d3js.org/d3.v3.min.js"></script> <script> var width = 960, size = 230, padding = 20; var x = d3.scale.linear() .range([padding / 2, size - padding / 2]); var y = d3.scale.linear() .range([size - padding / 2, padding / 2]); var xAxis = d3.svg.axis() .scale(x) .orient("bottom") .ticks(6); var yAxis = d3.svg.axis() .scale(y) .orient("left") .ticks(6); var color = d3.scale.category10(); d3.csv("https://gist.githubusercontent.com/mbostock/4063663/raw/13276d1a3d8e99e74c9fe33685da3afa6ed3a926/flowers.csv", function(error, data) { if (error) throw error; var domainByTrait = {}, traits = d3.keys(data[0]).filter(function(d) { return d !== "species"; }), n = traits.length; traits.forEach(function(trait) { domainByTrait[trait] = d3.extent(data, function(d) { return d[trait]; }); }); xAxis.tickSize(size * n); yAxis.tickSize(-size * n); var brush = d3.svg.brush() .x(x) .y(y) .on("brushstart", brushstart) .on("brush", brushmove) .on("brushend", brushend); var svg = d3.select("body").append("svg") .attr("width", size * n + padding) .attr("height", size * n + padding) .append("g") .attr("transform", "translate(" + padding + "," + padding / 2 + ")"); svg.selectAll(".x.axis") .data(traits) .enter().append("g") .attr("class", "x axis") .attr("transform", function(d, i) { return "translate(" + (n - i - 1) * size + ",0)"; }) .each(function(d) { x.domain(domainByTrait[d]); d3.select(this).call(xAxis); }); svg.selectAll(".y.axis") .data(traits) .enter().append("g") .attr("class", "y axis") .attr("transform", function(d, i) { return "translate(0," + i * size + ")"; }) .each(function(d) { y.domain(domainByTrait[d]); d3.select(this).call(yAxis); }); var cell = svg.selectAll(".cell") .data(cross(traits, traits)) .enter().append("g") .attr("class", "cell") .attr("transform", function(d) { return "translate(" + (n - d.i - 1) * size + "," + d.j * size + ")"; }) .each(plot); // Titles for the diagonal. cell.filter(function(d) { return d.i === d.j; }).append("text") .attr("x", padding) .attr("y", padding) .attr("dy", ".71em") .text(function(d) { return d.x; }); cell.call(brush); function plot(p) { var cell = d3.select(this); x.domain(domainByTrait[p.x]); y.domain(domainByTrait[p.y]); cell.append("rect") .attr("class", "frame") .attr("x", padding / 2) .attr("y", padding / 2) .attr("width", size - padding) .attr("height", size - padding); cell.selectAll("circle") .data(data) .enter().append("circle") .attr("cx", function(d) { return x(d[p.x]); }) .attr("cy", function(d) { return y(d[p.y]); }) .attr("r", 4) .style("fill", function(d) { return "#4682b4"; }); } var brushCell; // Clear the previously-active brush, if any. function brushstart(p) { if (brushCell !== this) { d3.select(brushCell).call(brush.clear()); x.domain(domainByTrait[p.x]); y.domain(domainByTrait[p.y]); brushCell = this; } } // Highlight the selected circles. function brushmove(p) { var e = brush.extent(); svg.selectAll("circle").classed("hidden", function(d) { return e[0][0] > d[p.x] || d[p.x] > e[1][0] || e[0][1] > d[p.y] || d[p.y] > e[1][1]; }); } function brushend(p) { // reset opacity svg.selectAll("circle").style('opacity', 1); // if no brush then bail if (brush.empty()) { svg.selectAll(".hidden").classed("hidden", false); return; } // some calculations var e = brush.extent(), xC = (e[1][0] + e[0][0]) / 2, yC = (e[1][1] + e[0][1]) / 2, // maxD is the maximum of the distance to the two edges maxD = Math.max( Math.sqrt((xC - e[0][0])**2), Math.sqrt ((yC - e[0][1])**2) ); // those circles not hidden svg.selectAll("circle:not(.hidden)") .transition() .duration(1000) .style("opacity", function(d) { // distance from furthest edge var xD = Math.sqrt( (xC - d[p.x])**2 + (yC - d[p.y])**2 ); // set opacity as percent of distance return (maxD - xD) / maxD; }); } }); function cross(a, b) { var c = [], n = a.length, m = b.length, i, j; for (i = -1; ++i < n;) for (j = -1; ++j < m;) c.push({x: a[i], i: i, y: b[j], j: j}); return c; } </script>
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