D3 v4 - SlopeChart

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge"/>
<title>D3 v4 - SlopeChart</title>
</head>

.Japan {
    fill:green;
    fill-opacity:1;
}
.valueLine.Japan {
    stroke:green;
}
</style>

<body>
<div id="wrapper">
    <svg></svg>    
</div>    
<script src="//cdnjs.cloudflare.com/ajax/libs/d3/4.1.1/d3.min.js"></script>    
<script>
function cast(d){
    Object.keys(d).forEach(function(key){
        if (!isNaN(+d[key])) d[key] = +d[key]
    })
    
    return d 
}

d3.tsv("gdp.tsv", cast, main)    
    
function main(data) {
    
    var slopeColumns = ["GDP_2000", "GDP_2015"]
    
    var domain = [500, 20000]
    var margin = {top:60, left:100, bottom:30, right:100}
    
    
    
    
    var width,height
    var plotWidth, plotHeight
    
    var svg = d3.select("svg")
    var plotLayer = svg.append("g").attr("class", "plotLayer")
    var slopeLeft = plotLayer.append("g").attr("class", "slopeLeft")
    var slopeRight = plotLayer.append("g").attr("class", "slopeRight")
    
    var xScale = d3.scalePoint().domain(slopeColumns)
    var yScale = d3.scaleLog().domain(domain)
    
    setSize()
    rendring(data)
    setReSizeEvent()    
        
    function rendring(data){
        renderAxis(data)
        renderSlope(data)
        renderLabel(data)
    }

function setSize() {
        width = svg.node().clientWidth
        height = svg.node().clientHeight
        
        plotWidth = width - (margin.left + margin.right)
        plotHeight = height - (margin.top + margin.bottom)
        
        plotLayer.attr("transform", "translate("+[margin.left, margin.top]+")")
            .attr("width", plotWidth)
            .attr("height", plotHeight)
                
        xScale.range([0, plotWidth])
        yScale.range([plotHeight, 0])

slopeLeft.attr("transform", "translate("+[xScale(slopeColumns[0]), 0]+")")
        slopeRight.attr("transform", "translate("+[xScale(slopeColumns[1]), 0]+")")

}
    
    function renderAxis(data) {
        //draw slopeAxis
        var selectedSlopeAxis = plotLayer.selectAll(".slopeAxis").data(slopeColumns)
        
        var newSlopeAxis = selectedSlopeAxis.enter().append("line")
            .attr("class", "slopeAxis")
            
        var slopeAxis = selectedSlopeAxis.merge(newSlopeAxis)
        
        slopeAxis
            .attr("x1", function(d){ return xScale(d)})
            .attr("y1", 0)
            .attr("x2", function(d){ return xScale(d)})
            .attr("y2", plotHeight)
            .attr("stroke", "black")
            
        //draw axisLable
        var selectedAxisLabel = plotLayer.selectAll(".AxisLabel").data(slopeColumns)
        
        var newAxisLabel = selectedAxisLabel.enter().append("text")
            .attr("class", "AxisLabel")
            .attr("text-anchor", "middle")
            .attr("dominant-baseline", "middle")
            
        var axisLabel = selectedAxisLabel.merge(newAxisLabel)
        
        axisLabel
            .attr("x", function(d){ return xScale(d)})
            .attr("y", "-2em")
            .text(function(d){ return d })
        
    }
        
    function renderSlope(data) {
        //draw valueLine
        var selectedValueLine = plotLayer.selectAll(".valueLine").data(data)
        
        var newValueLine = selectedValueLine.enter().append("line")
            .attr("class", function(d){ return "valueLine " + d["Country"]})
        
        var valueLine = selectedValueLine.merge(newValueLine)
        
        valueLine
            .attr("x1", xScale(slopeColumns[0]))
            .attr("y1", function(d){ return yScale(d[slopeColumns[0]])})
            .attr("x2", xScale(slopeColumns[1]))
            .attr("y2", function(d){ return yScale(d[slopeColumns[1]])})
            .attr("stroke", "black")
        
        
        //draw circle
        var selectedLeftCircle = slopeLeft.selectAll(".leftCircle").data(data)
        var selectedRightCircle = slopeRight.selectAll(".rightCircle").data(data)
        var newLeftCircle = selectedLeftCircle.enter().append("circle").attr("class",  function(d){ return "leftCircle " + d["Country"]})
        var newRigthCircle = selectedRightCircle.enter().append("circle").attr("class",  function(d){ return "rightCircle " + d["Country"]})
        var leftCircle = selectedLeftCircle.merge(newLeftCircle)
        var rightCircle = selectedRightCircle.merge(newRigthCircle)
        
        leftCircle.attr("cy", function(d){ return yScale(d[slopeColumns[0]]) }).attr("r", 4)
        rightCircle.attr("cy", function(d){ return yScale(d[slopeColumns[1]]) }).attr("r", 4)
        
        
    }
    
    function renderLabel(data) {
        //draw label
        var selectedLeftLabel = slopeLeft.selectAll(".leftLabel").data(data)
        var selectedRightLabel = slopeRight.selectAll(".rightLabel").data(data)
        
        var newLeftLabel = selectedLeftLabel.enter().append("text").attr("class", function(d){ return "leftLabel " + d["Country"] })
            .attr("text-anchor", "end")
            .attr("dominant-baseline", "middle")
        var newRigthLabel = selectedRightLabel.enter().append("text").attr("class", function(d){ return "rightLabel " + d["Country"] })
            .attr("text-anchor", "start")
            .attr("dominant-baseline", "middle")
        
        var leftLable = selectedLeftLabel.merge(newLeftLabel)
        var rightLable = selectedRightLabel.merge(newRigthLabel)
        
        leftLable.text(function(d){ return d["Country"] })
            .attr("x", "-0.5em")
            .attr("y", function(d){
                var y = yScale(d[slopeColumns[0]])
                if (d["Country"] === "China" || d["Country"] === "Mexico") y -= 6
                if (d["Country"] === "Italy" || d["Country"] === "Brazil") y += 6
                return  y})
        rightLable.text(function(d){ return d["Country"] })
            .attr("x", "0.5em")
            .attr("y", function(d){
                var y = yScale(d[slopeColumns[1]])
                if (d["Country"] === "Italy") y -= 6
                if (d["Country"] === "Brazil") y += 6
                return  y})
        
    }

</script>    
</body>
</html>

https://cdnjs.cloudflare.com/ajax/libs/d3/4.1.1/d3.min.js