Line chart in D3.js - parsing the date from JSON

Question

Right, so I'm trying to draw a simple line chart from a JSON source; but I am getting some errors which I can't figure out!

My d3.json() request should return :

[{"timestamp":1399325270,"value":-0.0029460209892230222598710528},{"timestamp":1399325271,"value":-0.0029460209892230222598710528},{"timestamp":1399325279,"value":-0.0029460209892230222598710528},....]

Here is my plotting script:

    var margin = { top: 20, right: 20, bottom: 30, left: 50 },
    width = document.getElementById("chartArea").offsetWidth - margin.left - margin.right,
    height = document.getElementById("chartArea").offsetHeight - margin.top - margin.bottom;

var parseDate = d3.time.format("%X");

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.timestamp); })
    .y(function (d) { return y(d.value); });

var svg = d3.select("#chartArea").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 + ")");

//var series = [];

d3.json("/cryptic/performance/benchmark/all", function (error, data) {
    data.forEach(function (d) {
        d.timestamp = parseDate((new Date(d.timestamp*1000)));
        d.value = (+d.value) * 100;
        //series.push([d.timestamp, d.value]);
    });

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

    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("Price ($)");

    console.log(data[0])

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

The error that I'm getting looks something like this:

Error: Problem parsing d="MNaN,451.6363636363636LNaN,451.6363636363636LNaN,451.6363636363636LNaN,451.6363636363636LNaN,451.6363636363636LNaN,451.6363636363636LNa....

depending on the size of the data but you get the point!

Any help is much appreciated as I have started to tear my hair out.

Answer 1

To change the axis labels, use axis.tickFormat() -- see e.g. this example.