linked DataViz

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3.v4.min.js"></script>
  <style>
    .axis path, .axis line {
      stroke: #ccc;
    }
    .axis line {
      stroke-dasharray: 2;
    }
    .axis text {
      fill: #ccc;
    }
    .state text {
      font-weight: 600;
    }
  </style>
</head>

<body>
  <script>
var width = 250;
var height = 200;
var margin = {top: 20, right: 30, bottom: 20, left: 30};
var xScale = d3.scaleLinear().range([0, width]);
var yScale = d3.scaleLinear().range([height, 0]);
var xAxis = d3.axisBottom()
	.scale(xScale)
	.ticks(5)
	.tickFormat(d => "'" + new String(d).slice(2))
	.tickSizeInner(-height)
	.tickSizeOuter(0)
	.tickPadding(6);
var yAxis = d3.axisLeft()
	.scale(yScale)
	.ticks(5)
	.tickFormat(d => d + '%')
	.tickSizeInner(-width)
	.tickSizeOuter(0)
	.tickPadding(6);
var line = d3.line()
	.x(d => xScale(d.year))
	.y(d => yScale(d.rate));
var red = '#d8472b';
var dispatch = d3.dispatch('load', 'yearchange')
    
d3.json('data.json', function(err, data) {
//   console.log(data);
  var flatData = [];
  data.forEach(obj => {
    var year = obj.date;
//     console.log(obj);
    for (key in obj){
//       console.log(key, obj[key])
      if (key !== 'date' && key !== 'avg' && key !== "D.C."){
      var state = key;
      var rate = obj[key];
      flatData.push({
        year:+year,
        state:state,
        rate: +rate,
      })              
    }
    }
  })
//   console.log(flatData);
  
  var xDomain = d3.extent(flatData, d => d.year)
  var yDomain = d3.extent(flatData, d => d.rate)
  xScale.domain(xDomain);
  yScale.domain(yDomain).nice();
//   console.log(xDomain, yDomain)
  
  var dataByState = d3.nest()
  	.key(d => d.state)
  	.entries(flatData);
//   console.log(dataByState);
  
  
   //create svg for each state
      var svg = d3.select('body')
      	.selectAll('svg')
      	.data(dataByState, d=> d.state)
      	.enter().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] + ')');
  
  
  
  dispatch.call('load', this, svg, dataByState);
  //default hovered year to 2016
  dispatch.call('yearchange', this, 2016)
  
});
    
    
   //draw the statis graph for each state
    dispatch.on('load.graph', (svg,dataByState) =>{
     
      //draw axes
      
      svg.append('g')
//       	.attr('class', 'x axis') --alernative to next line
      	.classed('x axis', true)
      	.attr('transform', 'translate(' + [0, height] + 				')')
      	.call(xAxis);
      
      
      svg.append('g')
      	.classed('y axis', true)
      	.call(yAxis);
   
    //draw lines   append + datum, selectAll + data
      svg.append('path')
      	.datum(d => d.values)
      	.attr('d', line)
      	.attr('stroke', '#c51b8a')
      	.attr('stroke-width', 2)
      	.attr('fill', 'none');
      	
     //draw rectagle for hover
      svg.append('rect')
      	.attr('width', width)
      	.attr('height', height)
      	.attr('opacity', 0)
      	.on('mousemove', function(){
        // x, y position of mouse relative to 
        //the container i pass in
            var [x,y] = d3.mouse(this);
        		var year = Math.round(xScale.invert(x));
//             console.log(x,year)
            dispatch.call('yearchange', this, year);
            
            
          });
      	});
    
dispatch.on('load.title', (svg) => {
  var title = svg.append('text');
  dispatch.on('yearchange.title', year => {
    title.text(d => {
      var rate = d.values.find(d => d.year === year);
      rate = rate ? d3.format('.1f')(rate.rate) + '%' : 'N/A';
      return d.key + ' (' + rate + ')';
    })
  })
});
  
 dispatch.on('load.point', svg =>{
          var g = svg.append('g');
          
          g.append('circle')
          	.attr('fill', 'red')
          	.attr('r', 5);
          
          g.append('text')
          	.attr('font-size', 10)
          
          dispatch.on('yearchange.point', year =>{
          g.attr('transform',d => {
          var rate = d.values.find(d => d.year === year);
            console.log(year)
          return 'translate(' + [xScale(rate.year), yScale(rate.rate)] + ')'
        });
        g.select('text')
          	.text(d => {
          var rate = d.values.find(d=>d.year === year);
          return rate.year + '(' + d3.format('.1f')(rate.rate) + '%)';
        });
        });
        });
    
    
  </script>
</body>

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