title: d3 scalelinear x axis only integer
body: <p>I get this error: "svg.append(...).attr(...).attr(...).call(...).tickFormat is not a function  </p>
  
  <pre><code>var x = d3.scaleLinear().domain([0, data.length]).range([0, width]);
  var y = d3.scaleLinear().domain([-1, 1]).range([height, 5]);
  // Add the X Axis
  svg.append("g")
      .attr("class", "x axis")
      .attr("transform", "translate(0," + y(0) + ")")
      .call(d3.axisBottom(x))
      .ticks(20)
      .tickFormat(d3.format(".0s"))
  </code></pre>
  
  <p>I want to put all the value of x axis to integer.</p>