README.md

10/21/2014 - 11:56 PM

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This is a six part series, taking you through stages of designing and creating reusable visualizations with d3.js

All visualizations have the same functionality, showcase the individual points with a bar chart and sum up the selected bars.

Part 5. This is showcasing the power of combining Backbone.js with d3.js and how to bind them together creating an abstraction between the visualization (the bar chart) and the rest of the application.

These are examples created for a talk (slides and video).

Cheers,

Miles @milr0c

index.html

<!DOCTYPE html>
  <head>
    <meta charset="utf-8">
    <link rel="stylesheet" type="text/css" href="http://littlesparkvt.com/flatstrap/assets/css/bootstrap.css"/>
    <link rel="stylesheet" type="text/css" href="style.css"/>
    <script src="http://code.jquery.com/jquery-2.0.0.min.js"></script>
    <script src="http://underscorejs.org/underscore-min.js"></script>
    <script src="http://backbonejs.org/backbone-min.js"></script>
    <script src="http://d3js.org/d3.v3.min.js"></script>
    <script src="src.js"></script>
  </head>
  <body>
    <div class="row">
      <div class="span2" id="helper"><button class="btn btn-success" id="update">update</button></div>
      <div class="span2" id="sum"></div>
    </div>
    <div class="row">
      <div id="chart"></div>
    </div>
    <script type="text/javascript">
// Models
var Point = Backbone.Model.extend({
  defaults: {
      x: 0,
      y: 0
  },
  type: "point",
});

var Sum = Backbone.Model.extend({
  defaults: {
    sum: 0
  }
});

// Collections
var Data = Backbone.Collection.extend({
  model: Point,
  extent: [0,0],
  x: d3.scale.ordinal(),
  sum: new Sum(),
  initialize: function() {
    this.fetch();
  },
  total: function() {
    var total = 0;
    this.forEach(function(d) {
      var xVal = d.get('x'),
          yVal = d.get('y');
      if (this.extent[0] <= this.x(xVal) && this.x(xVal) + this.x.rangeBand() <= this.extent[1]) {
        total += yVal;
      }
    }, this);
    this.sum.set('sum', total);
  },
  fetch: function() {
    this.randomize();
    this.extent = [0, 0];
    this.total();
  },
  randomize: function(n, y) {
    if (arguments.length < 2) y = 400;
    if (!arguments.length) n = 20;
    var i = 0;
    this.set(d3.range(~~(Math.random()*n) + 1).map(function(d, i) { return new Point({x: ++i, y: ~~(Math.random()*y)});
    }));
  },
});

// Views
var BarChart = Backbone.View.extend({
  el: "#chart",
  initialize: function() {
    this.collection.on("change reset add remove", this.render, this);
    var bar = charts.bar();
    var collection = this.collection;
    bar.on('brush', function(data) {
      collection.extent = d3.event.target.extent(),
      collection.x = bar.x();
      collection.total();
    });
    bar.on('brushend', function(data) {
      collection.extent = d3.event.target.extent(),
      collection.x = bar.x();
      collection.total();
    });
    bar.xValue(function(d) { return d.get('x'); });
    bar.yValue(function(d) { return d.get('y'); });
    this.bar = bar;
    this.render();
  },
  render: function() {
    d3.select(this.el) 
        .datum(this.collection.models)
        .call(this.bar);
  },
});

var HelperView = Backbone.View.extend({
  el: "#helper",
  events: {
    "click #update": "update",
  },
  update: function() {
    this.collection.fetch();
  }
});

var SumView = Backbone.View.extend({
  el: "#sum",
  initialize: function() {
    _.bindAll(this);
    this.model.bind('change', this.render);
    this.render();
  },
  render: function() {
    d3.select(this.$el.selector)
        .text('TOTAL: ' + this.model.get('sum'));
  }
});

// Main
var dataArr = new Data();
var barView = new BarChart({ collection: dataArr });
var helper = new HelperView({ collection: dataArr });
var sum = new SumView({ model: dataArr.sum });
    </script>
  </body>
</html>

src.js

charts = {};

charts.bar = function() {
  // basic data
  var margin = {top: 10, bottom: 20, left: 0, right: 0},
      width = 400,
      height = 400,
      // accessors
      xValue = function(d) { return d.x; },
      yValue = function(d) { return d.y; },
      // chart underpinnings
      brush = d3.svg.brush(),
      xAxis = d3.svg.axis().orient('bottom'),
      yAxis = d3.svg.axis().orient('left'),
      x = d3.scale.ordinal(),
      y = d3.scale.linear(),
      // chart enhancements
      elastic = {
        margin: true,
        x: true,
        y: true
      },
      convertData = true,
      duration = 500,
      formatNumber = d3.format(',d');

  function render(selection) {
    selection.each(function(data) {
      // setup the basics
      if (elastic.margin) margin.left = formatNumber(d3.max(data, function(d) { return d.y; })).length * 13;
      var w = width - margin.left - margin.right,
          h = height - margin.top - margin.bottom;

      // if needed convert the data
      if (convertData) {
        data = data.map(function(d, i) {
          return {
            x: xValue.call(data, d, i),
            y: yValue.call(data, d, i)
          };
        });
      }

      // set scales
      if (elastic.x) x.domain(data.map(function(d) { return d.x; }));
      if (elastic.y) y.domain([0, d3.max(data, function(d) { return d.y; })]);
      x.rangeRoundBands([0, w], .1);
      y.range([h, 0]);


      // reset axes and brush
      xAxis.scale(x);
      yAxis.scale(y);
      brush.x(x)
          .on('brushstart.chart', brushstart)
          .on('brush.chart', brushmove)
          .on('brushend.chart', brushend);
      brush.clear();

      var svg = selection.selectAll('svg').data([data]),
          chartEnter = svg.enter().append('svg')
                                  .append('g')
                                    .attr('width', w)
                                    .attr('height', h)
                                    .attr('transform', 'translate(' + margin.left + ',' + margin.top + ')')
                                    .classed('chart', true),
          chart = svg.select('.chart');

      chartEnter.append('g')
                .classed('x axis', true)
                .attr('transform', 'translate(' + 0 + ',' + h + ')');
      chartEnter.append('g')
                .classed('y axis', true)
      chartEnter.append('g').classed('barGroup', true);
      
      chart.selectAll('.brush').remove();
      chart.selectAll('.selected').classed('selected', false);
      
      chart.append('g')
                .classed('brush', true)
                .call(brush)
              .selectAll('rect')
                .attr('height', h);

      bars = chart.select('.barGroup').selectAll('.bar').data(data);

      bars.enter()
            .append('rect')
              .classed('bar', true)
              .attr('x', w) // start here for object constancy
              .attr('width', x.rangeBand())
              .attr('y', function(d, i) { return y(d.y); })
              .attr('height', function(d, i) { return h - y(d.y); });

      bars.transition()
            .duration(duration)
              .style('opacity', 1) // quick fix for exit problem
              .attr('width', x.rangeBand())
              .attr('x', function(d, i) { return x(d.x); })
              .attr('y', function(d, i) { return y(d.y); })
              .attr('height', function(d, i) { return h - y(d.y); });

      bars.exit()
            .transition()
                .duration(duration)
                    .style('opacity', 0)
                    .remove();

      chart.select('.x.axis')
            .transition()
                .duration(duration)
                  .call(xAxis);
      chart.select('.y.axis')
            .transition()
                .duration(duration)
                  .call(yAxis);  

      function brushstart() {
        chart.classed("selecting", true);
      }

      function brushmove() {
        var extent = d3.event.target.extent();
        bars.classed("selected", function(d) { return extent[0] <= x(d.x) && x(d.x) + x.rangeBand() <= extent[1]; });
      }

      function brushend() {
        chart.classed("selecting", !d3.event.target.empty());
      } 
    });
  }

  // basic data
  render.margin = function(_) {
    if (!arguments.length) return margin;
    margin = _;
    return render;
  };
  render.width = function(_) {
    if (!arguments.length) return width;
    width = _;
    return render;
  };
  render.height = function(_) {
    if (!arguments.length) return height;
    height = _;
    return render;
  };

  // accessors
  render.xValue = function(_) {
    if (!arguments.length) return xValue;
    xValue = _;
    return render;
  };
  render.yValue = function(_) {
    if (!arguments.length) return yValue;
    yValue = _;
    return render;
  };

  // chart underpinnings
  render.brush = function(_) {
    if (!arguments.length) return brush;
    brush = _;
    return render;
  };
  render.xAxis = function(_) {
    if (!arguments.length) return xAxis;
    xAxis = _;
    return render;
  };
  render.yAxis = function(_) {
    if (!arguments.length) return yAxis;
    yAxis = _;
    return render;
  };
  render.x = function(_) {
    if (!arguments.length) return x;
    x = _;
    return render;
  };
  render.y = function(_) {
    if (!arguments.length) return y;
    y = _;
    return render;
  };
  
  // chart enhancements
  render.elastic = function(_) {
    if (!arguments.length) return elastic;
    elastic = _;
    return render;
  };
  render.convertData = function(_) {
    if (!arguments.length) return convertData;
    convertData = _;
    return render;
  };
  render.duration = function(_) {
    if (!arguments.length) return duration;
    duration = _;
    return render;
  };
  render.formatNumber = function(_) {
    if (!arguments.length) return formatNumber;
    formatNumber = _;
    return render;
  };

  return d3.rebind(render, brush, 'on');
};

style.css

body {
  font: 14px helvetica;
  color: #f0f0f0;
  background-color: #333;
}

.row {
  padding: 5px;
  margin: 0px;
}

.axis path,
.axis line {
  fill: none;
  stroke: #f0f0f0;
  shape-rendering: crispEdges;
}

.axis text {
  fill: #f0f0f0;
}

.brush .extent {
  stroke: #f0f0f0;
  fill-opacity: .125;
  shape-rendering: crispEdges;
}

.bar {
  fill: #5EB4E3;
}
.selected {
  fill: #78C656;
}

thumbnail.png

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