d3.js creating a simple line chart with array of DateTime and int

Question

I am having trouble creating a simple line chart with an array of data.

I am getting the error: Error: attribute d: Expected number, "MNaN,NaNLNaN,NaNL…"

I brought this data in through c# and have converted to an array that looks like:

[
{date: "2017-08-15 16:00:00", high: "73.41", low: "73.2"},
{date: "2017-08-15 15:45:00", high: "73.38", low: "73.2715"},
{date: "2017-08-15 15:30:00", high: "73.33", low: "73.28"},
{date: "2017-08-15 15:15:00", high: "73.305", low: "73.185"},
{date: "2017-08-15 15:00:00", high: "73.22", low: "73.15"},
{date: "2017-08-15 14:45:00", high: "73.24", low: "73.1816"},
]

I am trying to graph the date on the x axis and the high on the y axis. I have found quite a few questions on this and I have referenced a couple below.

Draw D3 Simple Line chart With an Array

Creating a line graph from array of data objects

With my type() function i convert the 'date' objects to type DateTime and i convert the 'high' to a number. I then use render to show the graph.

@foreach (var i in Model.Data)
{
    <div>@i.Value.high</div>
}



<script>

    var arrayData = [];

var i in Model.Data)
    {
        @:arrayData.push({date : '@i.Key', high : '@i.Value.high', low : '@i.Value.low'});
    }


    var outerWidth = 500;
    var outerHeight = 500;
    var margin = { left: 30, top: 30, right: 30, bottom: 30 };
    var xColumn = "date";
    var yColumn = "high";

    // parse the date / time
    var parseTime = d3.timeParse("%d-%b-%y");

    //Create SVG element
    var svg = d3.select("body")
        .append("svg")
        .attr("width", outerWidth)
        .attr("height", outerHeight);

    //create a group
    var g = svg.append("g")
        .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

    //append a path element to our group
    var path = g.append("path");

    var innerWidth = outerWidth - margin.left - margin.right;
    var innerHeight = outerHeight - margin.top - margin.bottom;

    //set ranges
    var xScale = d3.scaleTime().range([0, innerWidth]);
    var yScale = d3.scaleLinear().range([innerHeight, 0]);

    //changed the below from d[xColumn] to d.date
    var line = d3.line()
        .x(function (d) { return xScale(d.xColumn); })
        .y(function (d) { return yScale(d.yColumn); });


    //changed the below from d[xColumn] to d.date
    function render(data) {
        xScale.domain(d3.extent(data, function (d) { return d.date; }));
        yScale.domain(d3.extent(data, function (d) { return d.high; }));
        path.attr("d", line(data));
    }

    function type(d) {
        d.date = new Date(d.date);
        d.date = parseTime(d.date);
        d.high = +d.high;
        d.low = + d.low;
        return d;
    }


    //below i have deterrmined that the type conversion is working by calling type() on the arrayData; i checked the arrayData.date before then after and saw it was converted to a object; I then checked
    //to see if this was an instance of a date
    console.log(arrayData.date);
    type(arrayData);

    var temp3 = (arrayData.date instanceof Date);
    console.log(temp3);

    var temp = typeof arrayData.date;
    var temp2 = typeof arrayData.high;
    console.log(temp);
    console.log(temp2);


    //try and run graph now
    render(arrayData);



</script>

After searching all over, to me it looks like I have the right format. I am new to d3 and can not figure out what I am doing wrong. Can someone help?

Mark · Accepted Answer · 2017-08-16 02:30:37Z

1

The way you are referencing your object's properties doesn't work in javascript.

You assign:

var xColumn = "date";
var yColumn = "high";

and then try to reference d.date and d.high with:

 .x(function (d) { return xScale(d.xColumn); })
 .y(function (d) { return yScale(d.yColumn); });

d.yColumn and d.xColumn will return undefined. If you want to reference them this way you need to use notation like: d[xColumn] and d[yColumn].

answered Aug 16, 2017 at 2:30

Mark

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3 Comments

JoeG Over a year ago

This did the trick! Thank you very much sir, I will accept this answer. In regards to the way I was referencing my objects I thought referencing through dot notation was allowed in javascript as stated here: w3schools.com/js/js_properties.asp

Mark Over a year ago

Glad it worked! dot notation does works, you just can't use a variable after the dot.

JoeG Over a year ago

I was plugging in 'numbers' on the x axis to get it working before. But as soon as I started using dates again on the x axis i get the error: '<path> attribute d: Expected number, "MNaN,72.084347120…" ' Do you know why this is? It seems as its still expecting a number on the x axis

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