how to format time on xAxis use d3.js

Question

According the demo on http://bl.ocks.org/mbostock/3883245

I don't know how format time on xAxis

this is my code : js:

    var data = [{
            "creat_time": "2013-03-12 15:09:04",
            "record_status": "ok",
            "roundTripTime": "16"
        }, {
            "creat_time": "2013-03-12 14:59:06",
            "record_status": "ok",
            "roundTripTime": "0"
        }, {
            "creat_time": "2013-03-12 14:49:04",
            "record_status": "ok",
            "roundTripTime": "297"
        }, {
            "creat_time": "2013-03-12 14:39:06",
            "record_status": "ok",
            "roundTripTime": "31"
        },{
            "creat_time": "2013-03-12 14:29:03",
            "record_status": "ok",
            "roundTripTime": "0"
    }];
    var margin = {top: 20, right: 20, bottom: 30, left: 50};
    var width = 960 - margin.left - margin.right;
    var height = 500 - margin.top - margin.bottom;
    var parseDate = d3.time.format("%Y-%m-%d %H:%M:%S").parse;
    var x = d3.time.scale()
        .range([0, width]);

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

    var xAxis = d3.svg.axis()
        .scale(x)
        .orient("bottom");

    var yAxis = d3.svg.axis()
        .scale(y)
        .orient("left");

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


    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 + ")");

    data.forEach(function(d) {
        d.creat_time = parseDate(d.creat_time);
        d.roundTripTime = +d.roundTripTime;
    });

    x.domain(d3.extent(data, function(d) { return d.creat_time; }));
    y.domain(d3.extent(data, function(d) { return d.roundTripTime;}));

    svg.append("g")
          .attr("class", "x axis")
          .attr("transform", "translate(0," + height + ")")
          .call(xAxis);

    svg.append("g")
          .attr("class", "y axis")
          .call(yAxis)
          .append("text")
          .attr("transform", "rotate(-90)")
          .attr("y", 6)
          .attr("dy", ".71em")
          .style("text-anchor", "end")
          .text("return time(ms)");

    svg.append("path")
          .datum(data)
          .attr("class", "line")
          .attr("d", line);

this is svg:

In svg , time is 12-hour clock ,but in my data time is 24-hour clock . how to keep the same format on svg and data?

Any help is appreciated. (ps:I hope you don't mind my English,it's so bad.)

Answer 1

You can use the tickFormat function on the axis object as below

var xAxis = d3.svg.axis()
    .scale(x)
    .orient("bottom")
    .tickFormat(d3.time.format("%H"));

The %H specifies hour (24-hour clock) as a decimal number [00,23]. Check this link D3 time formatting for more information

You can check out a working example in this tributary 24hr time example

Answer 2

The accepted answer is indeed correct, but in my case, I needed the flexibility for the formats to adjust to different scales (think zooming), but also to ensure the 24hr clock is used. The key is to define a multi-resolution time format. See the Documentation page for details.

My code:

var axisTimeFormat = d3.time.format.multi([
    [".%L", function(d) { return d.getMilliseconds(); }],
    [":%S", function(d) { return d.getSeconds(); }],
    ["%H:%M", function(d) { return d.getMinutes(); }],
    ["%H:%M", function(d) { return d.getHours(); }],
    ["%a %d", function(d) { return d.getDay() && d.getDate() != 1; }],
    ["%b %d", function(d) { return d.getDate() != 1; }],
    ["%B", function(d) { return d.getMonth(); }],
    ["%Y", function() { return true; }]
 ]);

var xAxis = d3.svg.axis()
    .scale(x)
    .orient("bottom")
    .tickFormat(axisTimeFormat);