Line chart with information box

Line chart with points hoover triggering updates of information box on the right.

<!DOCTYPE html>
<meta charset="utf-8">
<style>
.line {
  fill: none;
  stroke: steelblue;
  stroke-width: 1.5px;
}
</style>
<head>
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
</head>
<body>
    <script src="//d3js.org/d3.v4.min.js"></script>

<div class="row" style="width:860px;">    
            <div class="col-sm-9" id="g1"></div>
            <div class="col-sm-3" id="g2" ><br/><br /><br />
                <div id="point_info" class="alert" style="background-color:lightgray; visibility:hidden;">
                    <strong>Point Info!</strong><br/><br />
                    ID: <p id="point_id" style="display:inline;">...</p><br />
                    Value: <p id="point_value" style="display:inline;">...</p><br />
                </div>
            </div>
    </div>

function randomData(samples) {
        var data = [],
            random = d3.randomNormal();

for (i = 0; i < samples; i++) {
            data.push({
                id: i + 1,
                y: d3.format(".3")(random()) 
            });
        }
        return data;
    }

var data = randomData(200);

var margin = {top: 20, right: 20, bottom: 30, left: 50},
    width = 560 - margin.left - margin.right,
    height = 300 - margin.top - margin.bottom;

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

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

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

var svg = d3.select("#g1").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 + ")");

data.forEach(function (d) {
      Object.keys(data[0]).forEach(function (k) {
          d[k] = +d[k];
      });
  });

x.domain(d3.extent(data, function(d) { return d.id; }));
  y.domain(d3.extent(data, function (d) { return d.y; }));

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

var gY = svg.append("g")
      .attr("class", "axis axis--y")
      .call(d3.axisLeft(y));

svg.append("path")
      .datum(data)
      .attr("class", "line")
      .attr("d", line);

svg.selectAll(".dot")
                  .data(data)
                .enter().append("circle")
                  .attr("class", "dot")
                  .attr("r", 2.5)
                  .attr("cx", function (d) { return x(d.id); })
                  .attr("cy", function (d) { return y(d.y); })
                  .attr("opacity", 1)
  .on("mouseover", function (d) {
      d3.selectAll(".focus_circle").transition()
                    .duration(150).remove();
      svg.append("circle")
         .attr("class", "focus_circle")
         .attr("cx", x(d.id))
         .attr("cy", y(d.y))
         .attr("r", 5)
         .style("opacity", 1.0)
         .style("fill", "#f46d43");

d3.select("#point_info").transition()
                    .duration(700).style("visibility", "visible");
      d3.select("#point_id").html(d.id);
      d3.select("#point_value").html(d.y);
    
  });
</script>
</body>

https://d3js.org/d3.v4.min.js