Javascript 我在D3.JS中遇到了一些简单的问题

在可视化数据时，我遇到了一些折线图X轴的问题。 如图所示，X轴的线条消失了，实际上，它只显示了X轴的比例。我想知道为什么会出现这种情况。这是因为非法编码还是因为SVG的大小不够大，无法容纳整个画面

var margin = { top: 30, right: 120, bottom: 30, left: 50 },
    width = 960 - margin.left - margin.right,
    height = 600 - margin.top - margin.bottom,
    tooltip = { width: 100, height: 100, x: 10, y: -30 };

var parseDate = d3.timeParse("%m-%d-%Y"),
    bisectDate = d3.bisector(function(d) { return d.date; }).left,
    formatValue = d3.format(","),
    dateFormatter = d3.timeParse("%m-%d-%Y");

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

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

var xAxis = d3.axisBottom()
    
var yAxis = d3.axisLeft()
    .scale(y);

var line = d3.line()
    .x(function(d) { return x(d.date); })
    .y(function(d) { return y(d.likes); });

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("output4.csv", 
    function(d){
      return { date : d.framenum, likes : d.nSNR }
    },
    
  function(data) {

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

    svg.append("g")
        .attr("class", "x axis")
        .attr("transform", "translate(0," + height + ")")
        .call(d3.axisBottom(x));

    svg.append("g")
        .attr("class", "y axis")
        .call(yAxis)
        .style("font-size","17px")
        .append("text")
        .attr("transform", "rotate(-90)")
        .attr("y", 6)
        .attr("dy", ".71em")
        .style("text-anchor", "end")
        .text("Number of Likes");
        
    svg.append("path")
        .datum(data)
        .attr("class", "line")
        .attr("d", line);

    var focus = svg.append("g")
        .attr("class", "focus")
        .style("display", "none");

    focus.append("circle")
        .attr("r", 5);

    focus.append("rect")
        .attr("class", "tooltip")
        .attr("width", 100)
        .attr("height", 50)
        .attr("x", 10)
        .attr("y", -22)
        .attr("rx", 4)
        .attr("ry", 4);

    focus.append("text")
        .attr("class", "tooltip-date")
        .attr("x", 18)
        .attr("y", -2);

    focus.append("text")
        .attr("x", 18)
        .attr("y", 18)
        .text("Likes:");

    focus.append("text")
        .attr("class", "tooltip-likes")
        .attr("x", 60)
        .attr("y", 18);

    svg.append("rect")
        .attr("class", "overlay")
        .attr("width", width)
        .attr("height", height)
        .on("mouseover", function() { focus.style("display", null); })
        .on("mouseout", function() { focus.style("display", "none"); })
        .on("mousemove", mousemove);

    function mousemove() {
        var x0 = x.invert(d3.mouse(this)[0]),
            i = bisectDate(data, x0, 1),
            d0 = data[i - 1],
            d1 = data[i],
            d = x0 - d0.date > d1.date - x0 ? d1 : d0;
        focus.attr("transform", "translate(" + x(d.date) + "," + y(d.likes) + ")");
        focus.select(".tooltip-date").text(dateFormatter(d.date));
        focus.select(".tooltip-likes").text(formatValue(d.likes));
    }
});