	<!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("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 color(d.species); });
	}

	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];
	});
	}

	// If the brush is empty, select all circles.
	function brushend() {
	if (brush.empty()) svg.selectAll(".hidden").classed("hidden", false);
	}
	});

	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>