Bar Chart: stripped harder

This simple bar chart is constructed from a TSV file storing the frequency of letters in the English language. The chart employs conventional margins and a number of D3 features:

d3.tsv - load and parse data
d3.format - format percentages
d3.scale.ordinal - x-position encoding
d3.scale.linear - y-position encoding
d3.max - compute domains
d3.svg.axis - display axes

forked from mbostock's block: Bar Chart

forked from zanarmstrong's block: Bar Chart: stripped

<!DOCTYPE html>
<meta charset="utf-8">
<style>

.bar {
  fill: steelblue;
}

.bar:hover {
  fill: brown;
}

.axis {
  font: 10px sans-serif;
}

.axis path,
.axis line {
  fill: none;
  stroke: #000;
  shape-rendering: crispEdges;
}

.x.axis path {
  display: none;
}

</style>
<body>
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js"></script>
<script>
  
// INSTRUCTIONS: everywhere there is "xxxxx", replace with code - you might need to add other code

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

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 + ")");

d3.tsv("data.tsv", type, function(error, data) {
  if (error) throw error;

var letters = data.map(function(d) { return d.letter; });
  var maxFrequency = d3.max(data, function(d) { return d.frequency; })

svg.selectAll(".bar")
      .data(data)
    .enter().append("xxxxx")
  		"xxxxx"
  
});

function type(d) {
  d.frequency = +d.frequency;
  return d;
}

</script>

https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js