Chart Controls II

A little change from the previous one:

Adding grids
Path animated by transition, not the css opacity attribute.

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3.v3.min.js"></script>
  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
    .tick line,
    path.domain
    	{stroke: black;stroke-width: 1;fill: none;}
    .invisided{opacity: 0;}
    form{margin: 10px;padding: 5px;}
    label{display: inline-block;min-width: 80px;cursor:pointer;}
    .grid line{ stroke: #ccc;stroke-dasharray: 8, 8;}
  </style>
</head>

<body>
    <div id="container">
        <div>
          <form>
            <label><input name='country' type="radio" value="europe">Europe</label>
            <label><input name='country' type="radio" value="asia">Asia</label>
            <label><input name='country' type="radio" value="america">America</label>
          </form>
        </div>
    </div>
  <script>
    
    var margin = {top: 40, bottom: 40, left: 40, right: 40},
        svgHeight = 400, svgWidth = 500,
        Height = svgHeight - margin.top - margin.bottom,
        Width = svgWidth - margin.left - margin.right;

var dateParse = d3.time.format('%d-%b-%y').parse;

var xScale = d3.time.scale().range([0, Width]).nice(),
        yScale = d3.scale.linear().range([Height, 0]).nice(),

xAxis = d3.svg.axis().orient('bottom')
            .scale(xScale)
            .ticks(5)
            .tickFormat(d3.time.format('%b-%y')),
        yAxis = d3.svg.axis().orient('left')
            .scale(yScale).ticks(8),

colors = d3.scale.category10(),

xGrid = d3.svg.axis().orient('bottom')
            .scale(xScale)
            .ticks(5)
            .tickSize(-Height, 0)
            .tickFormat(''),
        yGrid = d3.svg.axis().orient('left')
            .scale(yScale)
            .ticks(8)
            .tickSize(-Width, 0)
            .tickFormat('');

var line = d3.svg.line()
        // .interpolate('basis')
        .x(function(d){return xScale(d.date);})
        .y(function(d){return yScale(d.value);});

var svg = d3.select('#container')
            .append('svg')
            .attr('width', svgWidth)
            .attr('height', svgHeight);

// radio inputs and events
    var inputs = d3.select('#container').selectAll('input')
    inputs.on('change', function(){
        var radioValue = document.forms[0]['country'].value;
        updata(radioValue);
    });

var url = 'data.tsv';
    var nestData, continents;

d3.tsv(url, function(error, data){
        // data proccessing
        continents = d3.keys(data[0])
            .filter(function(d){return d !== 'date'});
      
        var valExtent = [];

data.forEach(function(d){
            d.date    = dateParse(d.date);
            d.europe  = +d.europe;
            d.asia    = +d.asia;
            d.america = +d.america;
            valExtent = d3.extent([valExtent[0], valExtent[1],
                                   d.europe, d.asia, d.america]);
        });
        // nestData is global decleared
        nestData = continents.map(function(name){
            return {
                key: name,
                values: data.map(function(d){
                    return { date: d.date, value: d[name] };
                }),
            };
        });

// scale domain
        xScale.domain(d3.extent(data, function(d){return d.date;}));
        yScale.domain([valExtent[0] * 0.8, valExtent[1] * 1.1]);

// draw grids
        svg.append('g')
            .attr('class', 'grid')
            .attr('transform', 'translate(' +
                  [margin.left, margin.top + Height] + ')')
            .call(xGrid);
        svg.append('g')
            .attr('class', 'grid')
            .attr('transform', 'translate(' +
                  [margin.left, margin.top] + ')')
            .call(yGrid);
        // draw axises
        svg.append('g')
            .attr('transform', 'translate(' +
                  [margin.left, margin.top] + ')')
            .call(yAxis);
        svg.append('g')
            .attr('transform', 'translate(' +
                  [margin.left, margin.top + Height] + ')')
            .call(xAxis);
        // Main Line chart
        svg.append('g')
            .attr('transform', 'translate(' +
                  [margin.left, margin.top] + ')')
            .attr('class', 'graph');

// initial canvas
        // select the first input and set it checked
        d3.select('#container').select('input').property('checked', true);
        updata(document.forms[0]['country'].value);
    })

// drawing path funciton
    function updata(index){
        // get the data from index parameter
        var data = nestData[continents.indexOf(index)].values;

var ele = d3.select('svg .graph')
            .selectAll('path')
            .data(data);
        // update path according to new data
        ele
            .transition()
            .duration(300)
            .attr('d', line(data))
            .attr('stroke', colors(index));
        // if path is not exist, create a new one
        ele
            .enter()
            .append('path')
            .attr('d', line(data))
            .attr('fill', 'none')
            .attr('stroke-width', 3)
            .attr('stroke', colors(index));
        // if there is more tags then the data, kill the extra tags
        ele
            .exit()
            .remove();
    }

</script>
</body>

https://d3js.org/d3.v3.min.js