D3 Examples - Negative Relative Time Ticks

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<!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;
}
​
</style>
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script>
​
// This custom tick mark formatter displays signed hours and minutes
// relative to the given "zeroTime" date.
function relativeTimeFormatter(zeroTime){
  return function (d){
    
    var minutesNegative = d3.time.minutes(d, zeroTime).length;
    var minutesPositive = d3.time.minutes(zeroTime, d).length;
    var minutes = minutesNegative ? minutesNegative : minutesPositive;
    var hours = Math.floor(minutes / 60);
    var sign = minutesNegative ? "-" : "";
    
    hours = addLeadingZero(hours);
    minutes = (minutes % 60);
    minutes = addLeadingZero(minutes);
    
    return sign + hours + ":" + minutes;
  }
}
function addLeadingZero(number){
  return (number < 10 ? "0" : "") + number;
}
​
var parseTime = d3.time.format.utc("%H:%M").parse,
    zeroTime = parseTime("10:00");
​
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([
      
      // 3 hours before zero time.
      d3.time.hour.utc.offset(zeroTime, -3),
      
      // 2 hours after zero time.
      d3.time.hour.utc.offset(zeroTime, 2)
    ])
    .range([0, width]);
​
var y = d3.scale.linear()
    .range([height, 0]);
​
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(relativeTimeFormatter(zeroTime)));
​
  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);
});
  
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>
​
    