I have been trying to fill my circles with image of a country flag to show which circle represents which country but i have failed and any answer that i found it didn't worked. Here is my code.
JS script
d3.csv('dataVPcsvTest.csv', function (data) {
  // Variables
  var body = d3.select('body')
    var margin = { top: 100, right: 100, bottom: 100, left: 100 }
    var h = 1200 - margin.top - margin.bottom
    var w = 1200 - margin.left - margin.right
    // Scales
  var colorScale = d3.scale.category20()
  var xScale = d3.scale.linear()
    .domain([
        d3.min([0,d3.min(data,function (d) { return d.asd })]),
        d3.max([4000,d3.max(data,function (d) { return d.asd })])
        ])
    .range([0,w])
  var yScale = d3.scale.linear()
    .domain([
        d3.min([0,d3.min(data,function (d) { return d.aror })]),
        d3.max([1100,d3.max(data,function (d) { return d.aror })])
        ])
    .range([h,0])
    // SVG
    var svg = body.append('svg')
        .attr('height',h + margin.top + margin.bottom)
        .attr('width',w + margin.left + margin.right)
      .append('g')
        .attr('transform','translate(' + margin.left + ',' + margin.top + ')')
  // X-axis
    var xAxis = d3.svg.axis()
      .scale(xScale)
      .orient('bottom')
  // Y-axis
    var yAxis = d3.svg.axis()
      .scale(yScale)
    .orient('left')
  // Circles
  var circles = svg.selectAll('circle')
      .data(data)
      .enter()
    .append('circle')
      .attr('cx',function (d) { return xScale(d.asd) })
      .attr('cy',function (d) { return yScale(d.aror) })
      .attr('r','20')
      .attr('stroke','black')
      .attr('stroke-width',1)
      .attr('fill',function (d,i) { return colorScale(i)})
      .on('mouseover', function () {
        d3.select(this)
          .transition()
          .duration(500)
          .attr('r',30)
          .attr('stroke-width',3)
      })
      .on('mouseout', function () {
        d3.select(this)
          .transition()
          .duration(500)
          .attr('r',20)
          .attr('stroke-width',1)
      })
    .append('title') // Tooltip
      .text(function (d) { return d.state +
                           '\nKWh: ' + d.aror +
                           '\nGDP: ' + d.asd })
  // X-axis
  svg.append('g')
      .attr('class','axis')
      .attr('transform', 'translate(0,' + h + ')')
      .call(xAxis)
    .append('text') // X-axis Label
      .attr('class','label')
      .attr('y',-10)
      .attr('x',w)
      .attr('dy','.71em')
      .style('text-anchor','end')
      .text('GDP')
  // Y-axis
  svg.append('g')
      .attr('class', 'axis')
      .call(yAxis)
    .append('text') // y-axis Label
      .attr('class','label')
      .attr('transform','rotate(-90)')
      .attr('x',0)
      .attr('y',5)
      .attr('dy','.71em')
      .style('text-anchor','end')
      .text('Electric power consumption > KWh')
})
"state","aror","asd"
"Russia",927.21,1900.00
"India",835.5,1870.00
"Germany",579.21,3600.00
"Canada",565.73,1780.00
"South Korea",505.86,1110.00
"Brazil",480.12,2480.00
"France",476.5,2780.00
"United Kingdom",346.16,2440.00
"Italy",327.46,2190.00
"Spain",258.48,1480.00
"Mexico",249.67,1160.00
"Australia",239.31,1380.00
"Saudi Arabia",226.57,669.51
"Iran",199.79,514.06
"Turkey",197.94,774.78
"Ukraine",167.4,163.42
"Indonesia",165.71,846.48
"Thailand",154.19,345.67
"Poland",147.67,515.67
"Egypt",138.38,235.98
"Sweden",132.57,539.28
"Malaysia",122.12,287.93
"Argentina",120.86,446.04
"Netherlands",117.45,836.07
"Norway",114.78,491.06
"Venezuela",97.73,316.48
"Vietnam",94.28,141.67