D3 Examples - multiline_by

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<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3.v4.min.js"></script>
  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
  </style>
</head>
​
<body>
<select></select>
​
  <script>
var margin = {top: 10, right: 80, bottom: 70, left: 45},
    width = 960 - margin.left - margin.right,
    height = 500 - 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  g = svg.append("g").attr("transform", "translate(" + margin.left + "," + margin.top + ")");
​
//this isn't working right now
var parseTime = d3.timeParse("%y");
    
var line = d3.line()
    .x(function(d){return x(d[0])})
    .y(function(d){return y(d[1])})
//  .curve()
​
​
function filterJSON(json, location, dim){
        var result = [];
  json.forEach( function(val, idx, arr){
    if(val.name == location){
      result.push(val[dim])}
  })
    return result[0];
}
​
var x = d3.scaleLinear()
        .range([margin.left,width])
var y = d3.scaleLinear()
        .range([height,margin.bottom])
​
var data;
​
function drawGraph(data, dim){
  x.domain(d3.extent(data, function(d){return d[0]}))
  y.domain(d3.extent(data, function(d){return d[1]}))
  //appends x axis
  g.append("g")
    .attr("class", "axis axis--x")
    .attr("id", "xaxis")
    .attr("transform", "translate(0," + height + ")")
    .call(d3.axisBottom(x))
  // appends y axis
  g.append("g")
    .attr("class", "axis axis--y")
    .attr("id", "yaxis")
    .call(d3.axisLeft(y))
  .append("text")
      .attr("fill", "#000")
      .attr("transform", "rotate(-90)")
//       .attr("y", 6)
      .attr("dy", "0.71em")
      .attr("text-anchor", "end")
      .text(dim);  
  // appends line
  
    g.append("path")
    .datum(data)
    .attr("fill", "none")
    .attr("class","line")
    .attr("stroke", "steelblue")
    .attr("stroke-linejoin", "round")
    .attr("stroke-linecap", "round")
    .attr("stroke-width", 1.5)
    .attr("d", line);
}
    
    
d3.json("nations.json", function(error,json){
  if (error) throw error;
  
  function changeIt(){
    //get rid of everything and re-draw
        d3.selectAll(".line").remove()
      d3.selectAll("#yaxis").remove()
      d3.selectAll("#xaxis").remove()
    //get the value from the dropdown
        var sect = document.getElementById("ddSel");
      var country = sect.options[sect.selectedIndex].value;
      data_inc = filterJSON(json, country, "income")
      data_pop = filterJSON(json, country, "population")
      data_le = filterJSON(json, country, "lifeExpectancy")
      drawGraph(data_inc, form_val)      
            }
  var dropdown = d3.select("select")
    .attr("id", "ddSel");
  
  var options = dropdown.selectAll("option")
    .data(json)
    
  options.enter()
    .append("option")
    .text(function(d){return d.name})
        dropdown.on("change",changeIt)
    
​
//   this builds one line for angola income, initial graph
  data = filterJSON(json, "Angola", "income")
  data_pop = filterJSON(json, "Angola", "population")
  data_le = filterJSON(json, "Angola", "lifeExpectancy")
  drawGraph(data, "income")
  drawGraph(data_pop, "population")
  drawGraph(data_le, "lifeExpectancy")
  
  
});
​
  </script>
</body>
​
    