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@johan
Forked from mbostock/.block
Created July 20, 2016 11:52
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Sleep Cycles
license: gpl-3.0

This example shows how to plot daily time intervals in the style of Eric Boam’s Seven Months of Sleep. (The data here is fake.)

This graph uses a time scale to plot time-of-day along the y-axis. Time scales are normally used to plot absolute time: a specific moment on a specific day in a specific year. Here, though, we’re interested in studying the daily pattern, so the start and end times for each sleep interval are converted to offsets (elapsed times) relative to the midnight immediately preceeding the start time. Given an interval d:

var midnight = d3.utcDay.floor(d[0]),
    startOffset = d[0] - midnight,
    endOffset = d[1] - midnight;

The offsets are measured in milliseconds since that’s the JavaScript convention. To avoid inconsistencies across browser local time zones, the dates are represented as local times in the data but parsed as UTC. The resulting Date objects are inconsistent with the original dates, but the difference is irrelevant because we just want to plot the local time-of-day.

Also, this representation makes it easy to convert an offset back to an absolute time on an arbitrary day for using with a d3.scaleUtc and d3.utcFormat. The arbitrary day is the UNIX epoch:

function date(offset) {
  return new Date(offset);
}

A similar technique is used in my visualization of Eric Fischer’s Twitter feed.

#!/usr/bin/env node
var d3 = require("d3");
var hour = 36e5,
date0 = new Date(2016, 5, 1),
date1 = d3.timeMonth.offset(date0, 7),
timeFormat = d3.timeFormat("%Y-%m-%dT%H:%M:%S.%L"),
data = d3.timeDays(date0, date1).map(fakeDatum(22 * hour, 8 * hour, 0.5 * hour));
process.stdout.write(d3.csvFormat(data) + "\n");
function fakeDatum(offset, duration, deviation) {
var random = d3.randomNormal(0, deviation);
return function(date) {
return {
asleep: timeFormat(new Date(+date + random() + offset)),
awake: timeFormat(new Date(+date + random() + offset + duration))
};
};
}
<!DOCTYPE html>
<meta charset="utf-8">
<style>
.data {
fill: steelblue;
}
.axis--y .tick line {
stroke: #fff;
stroke-opacity: 0.8;
}
.axis--x .tick line {
stroke: #000;
stroke-opacity: 0.25;
}
.axis .domain {
display: none;
}
</style>
<svg width="960" height="500"></svg>
<script src="//d3js.org/d3.v4.min.js"></script>
<script>
var parseTime = d3.utcParse("%Y-%m-%dT%H:%M:%S.%L"),
formatHour = d3.utcFormat("%-I:%M %p"),
formatMonth = d3.utcFormat("%B");
var svg = d3.select("svg"),
margin = {top: 0, right: 0, bottom: 0, left: 70},
width = svg.attr("width") - margin.left - margin.right,
height = svg.attr("height") - margin.top - margin.bottom,
g = svg.append("g").attr("transform", "translate(" + margin.left + "," + margin.top + ")");
var x = d3.scaleUtc()
.rangeRound([0, width]);
var y = d3.scaleUtc()
.domain([date(19.65 * 36e5), date(32.35 * 36e5)]) // about 7:40 PM to 8:20 AM
.rangeRound([0, height]);
var area = d3.area()
.curve(d3.curveStepAfter)
.x(function(d) { return x(d.day); })
.y0(function(d) { return y(date(d[0] - d.day)); })
.y1(function(d) { return y(date(d[1] - d.day)); });
g.append("g")
.attr("class", "axis axis--y")
.call(d3.axisLeft(y)
.tickFormat(formatHour)
.tickSize(-width)
.tickPadding(10));
d3.csv("sleep.csv", type, function(error, data) {
if (error) throw error;
var date0 = data[0].day,
date1 = d3.utcDay.offset(data[data.length - 1].day, 1);
x.domain([date0, date1]);
g.append("g")
.attr("class", "axis axis--x")
.attr("transform", "translate(0," + height + ")")
.call(d3.axisBottom(x)
.tickFormat(formatMonth)
.tickSize(-height)
.tickPadding(-10))
.selectAll("text")
.attr("text-anchor", "start")
.attr("x", 10)
.attr("dy", null);
g.insert("path", ".axis")
.datum(data.concat({day: date1, 0: 0, 1: 0})) // for step-after
.attr("class", "data")
.attr("d", area);
});
function type(d) {
d = [parseTime(d.asleep), parseTime(d.awake)];
d.day = d3.utcDay.floor(d[0]);
return d;
}
function date(offset) {
return new Date(offset);
}
</script>
asleep awake
2016-06-01T22:00:11.942 2016-06-02T05:24:56.877
2016-06-02T22:06:38.621 2016-06-03T05:01:12.771
2016-06-03T21:22:08.347 2016-06-04T06:38:30.906
2016-06-04T21:59:35.031 2016-06-05T04:46:39.798
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2016-06-10T21:38:46.273 2016-06-11T04:49:54.359
2016-06-11T22:27:32.649 2016-06-12T06:03:21.422
2016-06-12T22:44:15.736 2016-06-13T07:09:17.746
2016-06-13T21:47:55.150 2016-06-14T06:28:54.528
2016-06-14T22:03:48.329 2016-06-15T05:21:41.680
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2016-10-12T21:45:58.205 2016-10-13T05:58:11.630
2016-10-13T22:39:35.008 2016-10-14T06:28:17.236
2016-10-14T21:56:13.389 2016-10-15T06:13:19.767
2016-10-15T22:10:25.083 2016-10-16T07:00:16.188
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2016-10-21T21:39:52.355 2016-10-22T06:06:02.845
2016-10-22T21:45:00.025 2016-10-23T06:03:11.832
2016-10-23T21:31:10.730 2016-10-24T06:20:06.396
2016-10-24T22:07:53.957 2016-10-25T06:33:50.358
2016-10-25T22:18:36.247 2016-10-26T05:45:12.212
2016-10-26T22:18:52.389 2016-10-27T05:59:50.223
2016-10-27T22:42:14.831 2016-10-28T06:12:57.580
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2016-10-31T21:47:08.478 2016-11-01T05:34:39.103
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2016-12-31T21:32:12.126 2017-01-01T06:43:38.269
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