Joukowsky在d3.js中变换-html代码片段

index.html
<!DOCTYPE html>
<meta charset="utf-8">
<style>
.line { fill: none; stroke: steelblue; stroke-width: 1.5px; }
</style>
<body>
<script src="http://d3js.org/d3.v3.min.js"></script>
<script>
    function Complex(re, im) { this.re  =   re; this.im  =   im; };
    Complex.prototype.clone = function(){ return new Complex(this.re,this.im); };
    Complex.prototype.add = function(z) { this.re += z.re; this.im += z.im; return this; };
    Complex.prototype.sub = function(z) { this.re -= z.re; this.im -= z.im; return this; };
    Complex.prototype.mul = function(z) 
    { 
        var tmp = this.re;
        this.re = this.re*z.re - this.im*z.im; 
        this.im =     tmp*z.im + this.im*z.re; 
        return this;
    };
                                                     
    Complex.prototype.div = function(z) 
    { 
        var tmp =  this.re, 
              n =     z.re*z.re +    z.im*z.im;
        this.re = (this.re*z.re + this.im*z.im)/n; 
        this.im = (   -tmp*z.im + this.im*z.re)/n; 
        return this;
    };
                                                     


    var width = 960, height = 500;

    var svg = d3.select("body")
                .append("svg")
                .attr("width",   width)
                .attr("height", height);

    var x = d3.scale.linear()
                    .range( [ 0, width])
                    .domain([-1,     3]);

    var y = d3.scale.linear()
                    .range( [height, 0])
                    .domain([    -2, 2]);

    var xAxis = d3.svg.axis().scale(x).orient("bottom");
    var yAxis = d3.svg.axis().scale(y).orient("left");

    var line = d3.svg.line()
                     .x(function(d) { return x(d.re); })
                     .y(function(d) { return y(d.im); });

    var data = d3.range(0,1,0.02).map(function(r){
               return d3.range(-Math.PI,Math.PI,Math.PI/50).map(function(p){
                      return new Complex(r*Math.cos(p)-0.2,r*Math.sin(p)+0.2);})})

    data.forEach(function(d){d.forEach(function(z) {z.add((new Complex(1,0)).div(z));})});

    svg.selectAll('path').data(data).enter().append('path').attr('class','line').attr('d',line);

</script>
</body>