D3.js rendering some circles

gistfile1.js

<script src="http://d3js.org/d3.v3.min.js"></script>
<script>

var margin = {top: 20, right: 20, bottom: 30, left: 40},
    width = 960 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom;

var formatPercent = d3.format(".0%");

var x = d3.scale.ordinal()
    .rangeRoundBands([0, width], .1);

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

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

var yAxis = d3.svg.axis()
    .scale(y)
    .orient("left")
    .tickFormat(formatPercent);

var svg = d3.select("body").append("svg")
    .attr("width", width + margin.left + margin.right)
    .attr("height", height + margin.top + margin.bottom)
  .append("g")
    .attr("transform", "translate(" + margin.left + "," + margin.top + ")");


  var data =[{letter: 'A', frequency: .1},
           {letter: 'B', frequency: .2},
     {letter: 'C', frequency: .5}			  
  ];

  x.domain(data.map(function(d) { return d.letter; }));
  y.domain([0, d3.max(data, function(d) { return d.frequency; })]);

  //x axis
  svg.append("g")
      .attr("class", "x axis")
      .attr("transform", "translate(0," + height + ")")
      .call(xAxis);
  //y axis
  svg.append("g")
      .attr("class", "y axis")
      .call(yAxis)
    .append("text")
      .attr("transform", "rotate(-90)")
      .attr("y", 6)
      .attr("dy", ".71em")
      .style("text-anchor", "end")
      .text("Frequency");

  //bars    
 /* svg.selectAll(".bar")
      .data(data)
    .enter().append("rect")
      .attr("class", "bar")
      .attr("x", function(d) {
      	return x(d.letter); 
      })
      .attr("width", x.rangeBand())
      .attr("y", function(d) { 
      	return y(d.frequency); 
      })
      .attr("height", function(d) { 
      	return height - y(d.frequency); 
      });
*/
  svg.selectAll("circle")
  	.data(data)
     .enter()
     .append("circle")
        .attr("class", "circle")
        .attr("r", function(d){ return d.frequency*100;})
        .style("fill", "pink")
              .style("stroke", "black")
        .style("stroke-width", "1.5")
        .text("blah")
        .attr("cx", function(d){ return d.frequency*100;})
        .attr("cy", function(d){return d.frequency*100;})
  
  

</script>