d3js - TypeError: string is undefined

Question

I don't understand this error:

TypeError: string is undefined function d3_time_parse(date, template, string, j) { var c, p, i = 0, n = template.length, m = string.length; ...

Here my code:

    var margin = {top: 20, right: 80, bottom: 30, left: 50},
        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]);

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

    var color = d3.scale.category10();

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

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

    var line = d3.svg.line()
        .interpolate("basis")
        .x(function(d) { return x(d.date); })
        .y(function(d) { return y(d.index); });

    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("data.csv", function(error, data) {
      color.domain(d3.keys(data[0]).filter(function(key) { return key !== "date"; }));

      data.forEach(function(d) {
        d.date = parseDate(d.date);
      });

      var indexes = color.domain().map(function(name) {
        return {
          name: name,
          values: data.map(function(d) {
            return {date: d.date, index: +d[name]};
          })
        };
      });

      x.domain(d3.extent(data, function(d) { return d.date; }));

      y.domain([
        d3.min(indexes, function(c) { return d3.min(c.values, function(v) { return v.index; }); }),
        d3.max(indexes, function(c) { return d3.max(c.values, function(v) { return v.index; }); })
      ]);

      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("Variation (%)");

      var index = svg.selectAll(".index")
          .data(indexes)
        .enter().append("g")
          .attr("class", "index");

      index.append("path")
          .attr("class", "line")
          .attr("d", function(d) { return line(d.values); })
          .style("stroke", function(d) { return color(d.name); });

      index.append("text")
          .datum(function(d) { return {name: d.name, value: d.values[d.values.length - 1]}; })
          .attr("transform", function(d) { return "translate(" + x(d.value.date) + "," + y(d.value.index) + ")"; })
          .attr("x", 3)
          .attr("dy", ".35em")
          .text(function(d) { return d.name; });
    });

and my csv file look like this:

Date,DAX,CAC40,FTSE,NASDAQ,Other
20060407,-0.000712859,-0.009013212,0.010819606,0.009846526,0.003082604
20060413,-0.007765968,-0.024263398,0.011238971,0.004128621,0.005952774
20060421,0.02261859,0.00330204,0.028734861,0.001688981,0.003459211
20060428,0.007170521,-0.007531405,0.010534438,-0.002416181,0.004012361
...

Could someone please help me? thx skeut

Answer 1

Date,DAX,CAC40,FTSE,NASDAQ,Other

JavaScript variable names are case sensitive, so when parsing CSV file with headers as above you need to refer to fields with:

d.Date // note the uppercase D
d.DAX // note all uppercase

Here's an example from d3 wiki https://github.com/mbostock/d3/wiki/CSV#wiki-parse

Year,Make,Model,Length

1997,Ford,E350,2.34

2000,Mercury,Cougar,2.38

When parsed with d3's CSV parser, the resulting data will be represented by the following array:

[
  {"Year": "1997", "Make": "Ford", "Model": "E350", "Length": "2.34"},
  {"Year": "2000", "Make": "Mercury", "Model": "Cougar", "Length": "2.38"}
]

Note the uppercase object keys. To access the year of the first entry, a "Year" with an uppercase Y in data[0].Year would be necessary.

Thus in your forEach function you'll need:

data.forEach(function (d) {
    d.Date = parseDate(d.Date);
});

... and later on:

return {date: d.Date, index: +d[name]};