score:2

Accepted answer

There are several problems in your code right now.

  1. You're using the variable data while setting your x and y domains. However that variable is not defined anywhere which is why the chart is not being generated.

  2. You're defining 2 arrays and trying to do the data mapping twice. You can remove the first step. Doing the following is sufficient.

    // directly map your data  
    chartData.forEach(function(d) {
      d.ethinicity = d[1];
      d.facebook_usage = +d[0];
    });
    

Check the embedded snippet below.

P.S. your x-axis positioning is off, you will probably want to adjust it.

var chartData = [
  [9.402974983096687, "Asian"],
  [10.762177012177013, "Black"],
  [12.213470319634704, "Chinese"],
  [11.211221431247658, "Hispanic"],
  [9.18421052631579, "American Indian"],
  [12.36144578313253, "Japanese"],
  [14.659334126040427, "Other"],
  [7.5, "Portuguese"],
  [10.636304446904095, "White"]
];

// No need to do the below

/*
var facebook_usage = [];
var ethinicity = [];

chartData.map(function(e, i) {
      facebook_usage.push(e[0]);
      ethinicity.push(e[1]);
    });
    //console.log(chartData);
    */

var margin = {
    top: 20,
    right: 20,
    bottom: 70,
    left: 40
  },
  width = 600 - margin.left - margin.right,
  height = 300 - margin.top - margin.bottom;


// set the ranges
var x = d3.scale.ordinal().rangeRoundBands([0, width], .05);

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

// define the axis
var xAxis = d3.svg.axis()
  .scale(x)
  .orient("bottom")


var yAxis = d3.svg.axis()
  .scale(y)
  .orient("left")
  .ticks(10);


// add the SVG element
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 + ")");


// load the data

// directly map your data here 
chartData.forEach(function(d) {
  d.ethinicity = d[1];
  d.facebook_usage = +d[0];
});

//console.log(chartData);

// scale the range of the data
x.domain(chartData.map(function(d) {
  return d.ethinicity;
}));
y.domain([0, d3.max(chartData, function(d) {
  return d.facebook_usage;
})]);

// add axis
svg.append("g")
  .attr("class", "x axis")
  .attr("transform", "translate(0," + height + ")")
  .call(xAxis)
  .selectAll("text")
  .style("text-anchor", "end")
  .attr("dx", "-.8em")
  .attr("dy", "-.55em")
  .attr("translate", "rotate(-90)");

svg.append("g")
  .attr("class", "y axis")
  .call(yAxis)
  .append("text")
  .attr("transform", "rotate(-90)")
  .attr("y", 5)
  .attr("dy", ".71em")
  .style("text-anchor", "end")
  .text("Frequency");


// Add bar chart
svg.selectAll("bar")
  .data(chartData)
  .enter().append("rect")
  .attr("class", "bar")
  .attr("x", function(d) {
    return x(d.ethinicity);
  })
  .attr("width", x.rangeBand())
  .attr("y", function(d) {
    return y(d.facebook_usage);
  })
  .attr("height", function(d) {
    return height - y(d.facebook_usage);
  });
.bar {
  fill: steelblue;
}

.bar:hover {
  fill: brown;
}

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

.axis path,
.axis line {
  fill: none;
  stroke: #000;
  shape-rendering: crispEdges;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.4.11/d3.min.js"></script>


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