Line Chart

<!doctype html>
<html lang="ja">
<head>
  <meta charset="UTF-8">
  <title>Line Chart</title>
<style>
  .axis path,
  .axis line{
    fill: none;
    stroke: black;
  }
  
  .axis line {
    opacity: 0.8;
    stroke-dasharray: 5 5;
  }

.tick text{
    font-size: 12px;
  }

.line{
    fill: none;
    stroke: blue;
    stroke-width: 2px;
  }
</style>
</head>
<body>
<script src="https://d3js.org/d3.v3.js"></script>
<script>

var margin = {top: 20, right: 100, bottom: 30, left: 100},
    width = 960 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom;

var dataset = [
  {x: 0, y: 5},
  {x: 1, y: 8},
  {x: 2, y: 13},
  {x: 3, y: 12},
  {x: 4, y: 16},
  {x: 5, y: 21},
  {x: 6, y: 18},
  {x: 7, y: 23},
  {x: 8, y: 24},
  {x: 9, y: 28},
  {x: 10, y: 35},
  {x: 11, y: 30},
  {x: 12, y: 32},
  {x: 13, y: 36},
  {x: 14, y: 40},
  {x: 15, y: 38},
];

var xScale = d3.scale.linear()
    .domain([0, d3.max(dataset, function(d){ return d.x; })])
    .range([0, width]);

var yScale = d3.scale.linear()
    .domain([0, d3.max(dataset, function(d){ return d.y; })])
    .range([height, 0]);

var xAxis = d3.svg.axis()
    .scale(xScale)
    .orient("bottom");

var yAxis = d3.svg.axis()
    .scale(yScale)
    .orient("left");

var line = d3.svg.line()
    .x(function(d) { return xScale(d.x); })
    .y(function(d) { return yScale(d.y); });

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)

svg.append("path")
      .datum(dataset)
      .attr("class", "line")
      .attr("d", line(dataset));
 	
  svg.selectAll("g").data(dataset).enter()
           .append("circle")
            .attr("cx", function(d) { return x(d.x) + 50; })
            .attr("cy", function(d) { return y(d.y); })
            .attr("r", 5)
            .style("fill", "black")
       
         .on("mouseover", function(d) {
                 d3.select(this).style("fill", "red")
                 svg.selectAll("path").data([d]).enter()
                    .append("line")
                    .style("stroke", "black")
                    .style("stroke-dasharray", ("2"))
                    .attr("id","line")
                    .attr("x1",function(d){return x(d.x)+50;})
                    .attr("y1",function(d){return y(d.y);}) 
                    .attr("x2",function(d){return x(d.x)+50;})
                    .attr("y2",400)
                 svg.selectAll("#tooltip").data([d]).enter()
                 		.append("text")
                    .text(function(d){return(d.value);})
                    .attr("id","tooltip")
                    .attr("x",function(d){return x(d.x)+50;})
                    .attr("y",function(d){return y(d.y)-25;})
                    .style("fill","green")
             })
       
            .on("mouseout", function(d){
              d3.select(this).style("fill","black")
              svg.selectAll("#line, #tooltip").data(data).remove()
            }); 
  
  svg.selectAll("g").data([dataset[dataset.length -1]]).enter()
       .append("text")
        .text(function(d, i) { return displayValue(d.y); })
        .attr("class", "line")
        .attr("y", function(d) { return y(d.y) })
        .attr("x", width - 20)
        .style("font-size", 20)
        .style("font-family", "monospace");

</script>
</body>
</html>

Modified http://d3js.org/d3.v3.js to a secure url

https://d3js.org/d3.v3.js