Simple d3.js graph with a json feed input

Question

I'm trying to draw a simple graph which gets its data from a json feed. The json feed looks like this:

[{"date":"2013-09-06","count":158},{"date":"2013-09-07","count":107},{"date":"2013-09-08","count":124},{"date":"2013-09-05","count":9},{"date":"2013-09-04","count":4},{"date":"2013-09-03","count":6},{"date":"2013-09-02","count":6},{"date":"2013-09-01","count":1}]

This is an example of the type of graph that I expect with the code below:

d3 graph

The JavaScript looks like this:

var margin = {top: 10, right: 10, bottom: 100, left: 400},
    width  = 960 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom;

var parseDate = d3.time.format("%Y-%m-%d").parse;

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

var xAxis = d3.svg.axis().scale(x).orient("bottom"),
    yAxis = d3.svg.axis().scale(y).orient("left");

var brush = d3.svg.brush().on("brush", brushed);

var area = d3.svg.area()
    .interpolate("monotone")
    .x(function(d) { return x(d.date); })
    .y0(height)
    .y1(function(d) { return y(d.count); });

var svg = d3.select("body").append("svg")
    .attr("width", width + margin.left + margin.right)
    .attr("height", height + margin.top + margin.bottom);

svg.append("defs").append("clipPath")
    .attr("id", "clip")
    .append("rect")
    .attr("width", width)
    .attr("height", height);

var focus = svg.append("g").attr("transform", "translate(" + margin.left + "," + margin.top + ")");

d3.json('http://path/to/feed.json', function (data) {
    data.forEach(function(d) {
      d.date = parseDate(d.date);
    });

  x.domain(d3.extent(data.map(function(d) { return d.date; })));
  y.domain([0, d3.max(data.map(function(d) { return d.count; }))]);

  focus.append("path")
       .datum(data)
       .attr("clip-path", "url(#clip)")
       .attr("d", area);

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

  focus.append("g")
       .attr("class", "y axis")
       .call(yAxis);
  });

  function brushed() {
    x.domain(brush.empty() ? x2.domain() : brush.extent());
    focus.select("path").attr("d", area);
    focus.select(".x.axis").call(xAxis);
  }

Update:

Got the graph to draw after fixing the bug Scott Cameron pointed out but it looks like this:

broken graph

Looks like the date parsing is acting up.

Can you try to describe what's going on? Is nothing displaying at all? You may not be loading the data. — bnjmn
– bnjmn, Commented Sep 8, 2013 at 13:47

Phuoc Do · Accepted Answer · 2013-09-09 05:39:29Z

2

Your JSON blob is out of order with time. If you sort your data points in correct time order, you'll get the correct graph.

http://vida.io/documents/ZkoBevX2ZGD8pCxZu

answered Sep 9, 2013 at 5:39

Phuoc Do

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2 Comments

railsuser400 Over a year ago

Yes that's so obvious now! Thank you. Any idea why the x-axis splits the dates and times into separate points? Even on your link.

Phuoc Do Over a year ago

It because there isn't enough data point to cover the entire x axis. I added a couple more points. Check the link again.

Scott Cameron · Accepted Answer · 2013-09-08 19:17:44Z

1

The y1 accessor on your area object is looking for d.price but it looks like there is no such property in your feed.

.y1(function(d) { return y(d.price); });

Should this be returning y(d.count)?

answered Sep 8, 2013 at 19:17

Scott Cameron

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2 Comments

railsuser400 Over a year ago

Spotted that as well. Ok so the graph works, but it's still weird. Slowly getting there... See updated question.

railsuser400 Over a year ago

Updated the JSON feed to reflect the exact one I'm consuming.

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