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@1wheel
Forked from mbostock/.block
Last active Dec 23, 2015
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Created for http://stackoverflow.com/questions/18809020/accessing-properties-of-objects-in-d3-histogram-bins

This chart shows a histogram of an Irwin–Hall distribution. The data is randomly generated. The values are then binned at regular intervals using D3’s histogram layout. The x-axis uses a linear scale, such that the tick values appear between bars; this provides better indication that each bar represents the count of values between its surrounding tick values.

See also this histogram of a log-normal distribution of time durations.

<!DOCTYPE html>
<meta charset="utf-8">
<style>
body {
font: 10px sans-serif;
}
.bar rect {
fill: steelblue;
shape-rendering: crispEdges;
}
.bar text {
fill: #fff;
}
.axis path, .axis line {
fill: none;
stroke: #000;
shape-rendering: crispEdges;
}
</style>
<body>
<script src="http://d3js.org/d3.v2.min.js?2.10.0"></script>
<script>
// Generate an Irwin–Hall distribution of 10 random variables.
var values = d3.range(50)
.map(d3.random.irwinHall(10))
.map(function(d){ return {score: d, name: "John Smith" + d}; });
// A formatter for counts.
var formatCount = d3.format(",.0f");
var margin = {top: 10, right: 30, bottom: 30, left: 30},
width = 960 - margin.left - margin.right,
height = 500 - margin.top - margin.bottom;
var x = d3.scale.linear()
.domain([0, 1])
.range([0, width]);
// Generate a histogram using twenty uniformly-spaced bins.
var data = d3.layout.histogram()
.bins(x.ticks(20))
(values.map(function(d){ return d.score; }));
var y = d3.scale.linear()
.domain([0, d3.max(data, function(d) { return d.y; })])
.range([height, 0]);
var xAxis = d3.svg.axis()
.scale(x)
.orient("bottom");
var svg = d3.select("body").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 + ")");
var bar = svg.selectAll(".bar")
.data(data)
.enter().append("g")
.attr("class", "bar")
.attr("transform", function(d) { return "translate(" + x(d.x) + "," + y(d.y) + ")"; });
bar.append("rect")
.attr("x", 1)
.attr("width", x(data[0].dx) - 1)
.attr("height", function(d) { return height - y(d.y); })
.on('mouseover',function(d){
console.log('data bound to bars ' + d);
console.log('names in bar ' +
values.filter(function(record){ return d.x <= record.score && record.score < d.x + d.dx; })
.map(function(record){ return record.name; }));
});
bar.append("text")
.attr("dy", ".75em")
.attr("y", 6)
.attr("x", x(data[0].dx) / 2)
.attr("text-anchor", "middle")
.text(function(d) { return formatCount(d.y); });
svg.append("g")
.attr("class", "x axis")
.attr("transform", "translate(0," + height + ")")
.call(xAxis);
</script>
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