title: draw a straight line between 2 coordinates in d3
body: <p>I have drawn x axis an y axis in d3.</p>
  
  <pre><code>var margin = {top: 20, right: 100, bottom: 30, left: 100},
      width = 960 - margin.left - margin.right,
      height = 500 - margin.top - margin.bottom;
  
  var xScale = d3.scale.linear()
      .domain([0, 15])
      .range([0, width]);
  
  var yScale = d3.scale.linear()
      .domain([0, 38])
      .range([height, 0]);
  
  var xAxis = d3.svg.axis()
      .scale(xScale)
      .orient("bottom")
      .innerTickSize(-height)
      .outerTickSize(0)
      .tickPadding(10);
  
  var yAxis = d3.svg.axis()
      .scale(yScale)
      .orient("left")
      .innerTickSize(-width)
      .outerTickSize(0)
      .tickPadding(10);
  
  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 + ")");
  
    svg.append("g")
        .attr("class", "x axis")
        .attr("transform", "translate(0," + height + ")")
        .call(xAxis);
  
    svg.append("g")
        .attr("class", "y axis")
        .call(yAxis);
  </code></pre>
  
  <p>I then want to draw a line between 2 points in this grid.</p>
  
  <pre><code>  svg.append('line')
        .style('stroke', 'black')
        .attr('x1', 5)
        .attr('y1', 5)
        .attr('x2', 20)
        .attr('y2', 20);
  </code></pre>
  
  <p>Here is a <a href="http://jsbin.com/sewaqo/1/edit?js,output" rel="nofollow">jsbin</a> of the results.</p>
  
  <p>So the line is not drawn between the grid coordinates (5, 5) and (20, 20).</p>
  
  <p>How can I place the line on the coordinates of the grid that I have created?</p>