D3 x轴显示不正确

Question

I'm trying to create a bar chart with data achieved from JSON. This was working properly in my test drive, that had data from csv, but I'm having problem showing the x-axis in my graph. Here is how it's currently displayed:

var svg = d3.select("svg"),
margin = {top: 20, right: 20, bottom: 30, left: 40},
width = +svg.attr("width") - margin.left - margin.right,
height = +svg.attr("height") - margin.top - margin.bottom;

var x = d3.scaleOrdinal().range([0, width]);
var y = d3.scaleLinear().rangeRound([height, 0]);


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

d3.json(urljson, function(error, data) {
    data = data.results;
data.forEach(function(d) {
    d.result = +d.result;
});
console.log(data);

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

g.append("g")
    .attr("class", "axis axis--x")
    .attr("transform", "translate(0," + (height) + ")")
    .call(d3.axisBottom(x));
console.log(x.domain());
console.log(y.domain());

g.append("g")
    .attr("class", "axis axis--y")
    .call(d3.axisLeft(y))
    .append("text")
    .attr("transform", "rotate(-90)")
    .attr("y", 6)
    .attr("dy", "0.71em")
    .attr("text-anchor", "end")
    .text("Value");

g.selectAll(".bar")
    .data(data)
    .enter()
    .append("rect")
        .attr("class", "bar")
        .attr("x", function(d) {return x(d.date); })
        .attr("y", function(d) {return y(d.result); })
        .attr("height", function(d) {return height - y(d.result);})
});

and the JSON I am using looks like this:

{
"count": 5,
"next": null,
"previous": null,
"results": [
    {
        "date": "2017-09-22",
        "result": 35.9
    },
    {
        "date": "2017-09-23",
        "result": 65.12
    },
    {
        "date": "2017-09-24",
        "result": 11.23
    },
    {
        "date": "2017-09-25",
        "result": 77.8
    },
    {
        "date": "2017-09-26",
        "result": 108.98
    }
]
}

Answer 1

Since x is an ordinal scale, you have to set a range with the same number of elements of the domain. According to the API:

If there are fewer elements in the range than in the domain, the scale will reuse values from the start of the range. (emphasis mine)

This is a demo, that shows the behaviour of your code: all the values in the domain will be printed at 0 or width :

 var svg = d3.select("svg"); var scale = d3.scaleOrdinal() .domain(["foo", "bar", "baz", "foobar", "foobaz"]) .range([10, 290]) var xAxis = d3.axisBottom(scale); svg.append("g") .attr("transform", "translate(0,50)") .call(xAxis); 

 <script src="https://d3js.org/d3.v4.min.js"></script> <svg></svg> 

Solution : An easy alternative is using a band scale (or a point scale, depending on your goals). So, it should be:

var x = d3.scaleBand().range([0, width]);

This is the same code using a band scale:

 var svg = d3.select("svg"); var scale = d3.scaleBand() .domain(["foo", "bar", "baz", "foobar", "foobaz"]) .range([10, 290]) var xAxis = d3.axisBottom(scale); svg.append("g") .attr("transform", "translate(0,50)") .call(xAxis); 

 <script src="https://d3js.org/d3.v4.min.js"></script> <svg></svg> 

PS: I see that in your code your rectangles have no width. If you decide to use the band scale, you can do:

.attr("width", x.bandwidth())