Spurious Correlations Dual Axis Line Chart

Rough recreation of the "per capita consuption of mozzarella cheese & civil engineering doctorates awarded" correlation plot from Spurious Correlations blog (http://www.tylervigen.com/spurious-correlations)

<!DOCTYPE html>
<meta charset="utf-8">

:root {
    --highlight-color:red;
}

.axis .tick {
  stroke-width:0.5px;
  stroke-opacity: .5;
}

.axis path {
  stroke: none;
}

.line {
  stroke: black;
  fill: none;
  stroke-width: 1.5;
}

.axis.cheese text {
  fill: var(--highlight-color);
}

.cheese-circle {
  fill: var(--highlight-color);
}

.line.cheese {
  stroke: var(--highlight-color);
}

</style>

var margin = {top: 20, right: 40, bottom: 30, left: 40};

var width = 900 - margin.left - margin.right,
    height = 250 - margin.top - margin.bottom;

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 + ")");

var xScale = d3.scaleLinear()
  .domain([1999, 2010])
  .range([0, width]);

var cheeseScale = d3.scaleLinear()
  .domain([9, 12])
  .range([height, 0]);

var doctorateScale = d3.scaleLinear()
  .domain([400, 1000])
  .range([height, 0])

var xAxis = d3.axisBottom(xScale)
  .tickFormat(d3.format("d"));

var cheeseAxis = d3.axisLeft(cheeseScale)
  .ticks(4)
  .tickSize(-width);

var doctorateAxis = d3.axisRight(doctorateScale)
  .ticks(4)
  .tickSize(0);

d3.csv("cheese_engineers.csv", ready)

function ready(error, data) {

if (error) return console.warn(error);

svg.append('g')
    .attr('class', 'x axis')
    .attr('transform', 'translate(0, ' + height + ')')
    .call(xAxis)

svg.append('g')
    .attr('class', 'cheese axis')
    .call(cheeseAxis)

svg.append('g')
    .attr('class', 'doctorate axis')
    .attr('transform', 'translate(' + width + ', 0)')
    .call(doctorateAxis)

function select_year(d) {
    var this_year = 'year' + d.year;
    d3.select(".details").text('In ' + d.year + ', ' + d.cheese + ' pounds of mozzarella cheese was consumed, and ' + d.doctorates + ' Civil Engineering Doctorates were awarded')
    d3.selectAll('.circle')
      .attr('r', 5)
    d3.selectAll('.' + this_year)
      .transition()
      .attr('r', 15)
  }

function deselect_year(d) {
    d3.selectAll('.circle')
      .transition()
      .attr('r', 5)
  }

var cheeseCircle = svg.selectAll('.cheese-circle')
    .data(data)
   .enter().append('circle')
     .attr('class', 'cheese-circle')
     .attr("class", function(d) { return 'cheese-circle circle ' + 'year' + d.year })
     .attr('r', 5)
     .attr('cx', function(d) { return xScale(d.year) })
     .attr('cy', function(d) { return cheeseScale(d.cheese)})
     .attr('fill', 'red')
     .on('mouseover', function(d) {
        select_year(d)
      })
      .on('mouseout', function(d) {
        deselect_year(d)
      });

var cheeseLineGenerator = d3.line()
    .x(function(d) { return xScale(d.year) })
    .y(function(d) { return cheeseScale(d.cheese)})

var cheesePath = svg.append('path')
    .datum(data)
    .attr('class', 'line')
    .attr('d', cheeseLineGenerator(data))
    .style('stroke', 'red')

var doctorateCircle = svg.selectAll('.doctorate-circle')
    .data(data)
    .enter().append('circle')
    .attr("class", function(d) { return 'doctorate-circle circle ' + 'year' + d.year })     .attr('r', 5)
    .attr('cx', function(d) { return xScale(d.year) })
    .attr('cy', function(d) { return doctorateScale(d.doctorates)})
    .on('mouseover', function(d) {
      select_year(d)
    })
    .on('mouseout', function(d) {
      deselect_year(d)
    });

var doctorateLineGenerator = d3.line()
    .x(function(d) { return xScale(d.year) })
    .y(function(d) { return doctorateScale(d.doctorates)})

var doctoratePath = svg.append('path')
    .datum(data)
    .attr('class', 'line')
    .attr('d', doctorateLineGenerator(data));

svg.append("text")
    .attr("transform", "rotate(-90)")
    .attr("y", 0 - margin.left)
    .attr("x",0 - (height / 2))
    .attr("dy", "1em")
    .style("text-anchor", "middle")
    .text("Mozzarella cheese consumption (lbs)")
    .attr('fill', 'red');

svg.append("text")
    .attr("transform", "rotate(-90)")
    .attr("y", width + 20)
    .attr("x",0 - (height / 2))
    .attr("dy", "1em")
    .style("text-anchor", "middle")
    .text("Civil Engineering Doctorates");   
}

</script>

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