Tweet Times with LOESS Curve

This graph plots the observed rate of tweets for Eric Fischer’s Twitter feed over the period from January 8, 2015 through November 30, 2015 with a LOESS curve fitted to the data using science.js.

Forked from mbostock's block: Time of Day

Draws from the example Loess with science.js for adding the LOESS curve.

Part of a discussion on d3-shape: Moving averages, line smoothing, etc. #43.

<!DOCTYPE html>
<meta charset="utf-8">
<style>

.dots path {
  fill: none;
  stroke: steelblue;
  stroke-width: 1.5px;
}

.axis path,
.axis line {
  fill: none;
  stroke: #000;
  shape-rendering: crispEdges;
}

.axis--y line {
  stroke-opacity: 0.2;
}

.axis--y path {
  stroke: none;
}

.axis text {
  font: 10px sans-serif;
}

.loess {
  stroke: #000;
  stroke-width: 3px;
  fill: none;
}

</style>
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script src="science.v1.min.js"></script>
<script>

var parseTime = d3.time.format.utc("%H:%M").parse,
    midnight = parseTime("00:00");

var margin = {top: 30, right: 30, bottom: 30, left: 30},
    width = 960 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom;

var x = d3.time.scale.utc()
    .domain([midnight, d3.time.day.utc.offset(midnight, 1)])
    .range([0, width]);

var y = d3.scale.linear()
    .range([height, 0]);

var line = d3.svg.line()
    .x(function(d) { return x(d.time); })
    .y(function(d) { return y(d.rateSmooth); });

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 + ")");

d3.csv("tweets.csv", type, function(error, data) {
  if (error) throw error;

y.domain([0, d3.max(data, function(d) { return d.rate; })]);

svg.append("g")
      .attr("class", "axis axis--x")
      .attr("transform", "translate(0," + height + ")")
      .call(d3.svg.axis()
          .scale(x)
          .orient("bottom")
          .tickFormat(d3.time.format.utc("%I %p")));

svg.append("g")
      .attr("class", "dots")
    .selectAll("path")
      .data(data)
    .enter().append("path")
      .attr("transform", function(d) { return "translate(" + x(d.time) + "," + y(d.rate) + ")"; })
      .attr("d", d3.svg.symbol()
          .size(40));

var tick = svg.append("g")
      .attr("class", "axis axis--y")
      .call(d3.svg.axis()
          .scale(y)
          .tickSize(-width)
          .orient("left"))
    .select(".tick:last-of-type");

var title = tick.append("text")
      .attr("dy", ".32em")
      .text("tweets per hour");

tick.select("line")
      .attr("x1", title.node().getBBox().width + 6);

var loess = science.stats.loess().bandwidth(.1);

data.sort(function (a, b){ return a.time < b.time ? -1 : 1 });

var xValues = data.map(function (d){ return d.time; });
  var yValues = data.map(function (d){ return d.rate; });

var pathData = loess(xValues, yValues).map(function (yValue, i){
    return {
      time: data[i].time,
      rateSmooth: yValue
    };
  });

svg.selectAll(".loess")
      .data([pathData])
    .enter().append("path")
      .attr("class", "loess")
      .attr("d", line); 
});

function type(d) {
  d.rate = +d.count / 327 * 60; // January 8 to November 30
  d.time = parseTime(d.time);
  d.time.setUTCHours((d.time.getUTCHours() + 24 - 7) % 24);
  return d;
}

</script>

https://d3js.org/d3.v3.min.js