title: Issue with d3 Multi Line Chart
body: <p>I didn't get line throw this code,
  i get perfect  axis both side but line is still missing </p>
  
  <p>while calling drawline function i got this errorr "Error:  attribute d: Expected number, "M0,NaNL116.66666666…"." </p>
  
  <p>i couldn't find out any solutions.</p>
  
  <pre><code>&lt;script src="http://d3js.org/d3.v4.min.js"&gt;&lt;/script&gt;
  
      //Data from Webservice
      var jsonData = [{ "YEAR": "2017", "JAN": "0", "FEB": "21", "MAR": "65", "APR": "25", "MAY": "33", "JUN": "30", "JUL": "17", "AUG": "26", "SEP": "0", "OCT": "5", "NOV": "33", "DEC": "12" }, { "YEAR": "2018", "JAN": "10", "FEB": "0", "MAR": "0", "APR": "0", "MAY": "0", "JUN": "0", "JUL": "0", "AUG": "0", "SEP": "0", "OCT": "0", "NOV": "0", "DEC": "0" }]; `
  
          var x = d3.scaleBand().range([0, width]);           
          var y = d3.scaleLinear().range([height, 0]);
  
          var tests = months.map(function (m) {`
      return {
          month: m,
          values: jsonData.map(function (d) {
              return {
                  year: d.YEAR,
                  quote: +d[m]
              };
          })
      };
                  });
  
  
      x.domain(tests.map(function (d) { return d.month; }));
      y.domain([d3.min(tests, function (c) {
          return d3.min(c.values, function (v) {
              return v.quote;
          });
      }),
      d3.max(tests, function (c) { return d3.max(c.values, ` `function (v) { return v.quote; }); })]);
  
  
      // Create Line
  
      var drawLine = d3.line()
          .curve(d3.curveBasis)
          .x(function (d) {
              debugger;
              return x(d.month);
          })
          .y(function (d) {
              debugger;
              return y(d.values);
          });
  
      var draw = svg.selectAll(".month")
          .data(tests)
          .enter().append("g")
          .attr("class", "month")
          .datum(tests)
          .append("path")
          .attr("class", "line")
          .attr("d", drawLine)
          .style("stroke", function (d) {
              return color(d.year);
          })
  </code></pre>
  
  <p>`</p>