Barley Line Chart

<!DOCTYPE html>
<meta charset="utf-8">
<style>
.lines {
  fill: none;
}
</style>
<script src="https://d3js.org/d3.v4.min.js"></script>
<body>
<script>

var margin = {top: 20, right: 40, bottom: 30, left: 50};

var width = 800 - margin.left - margin.right,
    height = 350 - margin.top - margin.bottom;

var xScale = d3.scalePoint()
    .rangeRound([0, width])

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

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 color = d3.scaleOrdinal(d3.schemeCategory20c);

d3.tsv("barley.tsv", function(error, data) {

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

data = data.filter(function(d)  { return d.site == "Morris"} );
  data.forEach(function(d) {
    d.yield = +d.yield;
  })

yScale.domain([0, d3.max(data, function(d) { return d.yield })])
  xScale.domain(d3.set(data.map(function(d) { return d.variety })).values())

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

svg.append("g")
      .attr("class", "y axis")
      .call(d3.axisLeft(yScale));

var dots = svg.selectAll(".dots")
      .data(data)
    .enter().append("circle")
      .attr("class", "dots")
      .attr("r", 5)
      .attr("cx", function(d) { return xScale(d.variety) })
      .attr("cy", function(d) { return yScale(d.yield) })
      .style("fill", function(d) { return color(d.year) })

var nestedData = d3.nest()
      .key(function(d) { return d.year })
      .entries(data);

var lineGenerator = d3.line()
      .x(function(d) { return xScale(d.variety) })
      .y(function(d) { return yScale(d.yield) })

svg.selectAll(".lines")
    .data(nestedData)
  .enter().append("path")
    .attr("class", "lines")
    .style("stroke", function(d) {return color(d.key) })
    .attr("d", function(d) { return lineGenerator(d.values) })

});

</script>

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