population v GDP

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<head>
  <meta charset="utf-8">
  <title>SVG intro</title>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js"></script>
 
  <style>
    circle {
      fill-opacity:0.5;
      stroke-opacity:0.5;
    }
   
  </style>
	
</head>

<body>
  
  
  <script>
   
    var outerWidth = 300;
    var outerHeight = 250;
    var margin = { left: 30, right:30, top:30, bottom:30};
    
    var innerWidth = outerWidth - margin.left - margin.right;
    var innerHeight = outerHeight - margin.top - margin.bottom;
    var circleRadius = 5;
    var xColumn = "population";
    var yColumn = "gdp";
    var rColumn = "population";
    var rMin = 0; rMax = 20;
    var r = 2;
    
    var svg = d3. select("body").append("svg")
    	.attr("width", outerWidth)
    	.attr("height", outerHeight);
    
    var g = svg.append('g')
    	.attr('transform',"translate(" + margin.left + ", " + margin.top + ")");
    
    var xScale = d3.scale.log().range([0,innerWidth]);
    var yScale = d3.scale.log().range([innerHeight,0]);
    var rScale = d3.scale.sqrt().range([rMin,rMax]);  // make the area of the circle proportional to the size of the circle.

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