D3 + Backbone
=
Reusable Charts


@jtuulos

May 9, 2013

This talk on YouTube

UPDATE 10/20/2013: See also AdRoll/backbone.d3

Why reusable charts?

Modularity
Abstraction
Maintenance
Collaboration

Web frameworks & D3

Server-side framework + D3

Header

List

Item

D3 chart

Item

D3 chart

Client-side framework + D3

Header

ListView

ItemView

D3 chart

ItemView

D3 chart

Helpful methods to manipulate and query your data

"Backbone is a library, not a framework"

Plays well with others

(from the official FAQ)

Goal: Spreadsheet charts

Goal: JSON + Backbone + D3


var json = [
  {"letter": "A", "frequency": 0.08167, ... },
  {"letter": "B", "frequency": 0.01492, ... },
  {"letter": "C", "frequency": 0.02780, ... },
  {"letter": "D", "frequency": 0.04253, ... },
  {"letter": "E", "frequency": 0.12702, ... },
  {"letter": "F", "frequency": 0.02288, ... },
  {"letter": "G", "frequency": 0.02022, ... },
  {"letter": "H", "frequency": 0.06094, ... },
  {"letter": "I", "frequency": 0.06973, ... },
  {"letter": "J", "frequency": 0.00153, ... },
  {"letter": "K", "frequency": 0.00747, ... },
  {"letter": "L", "frequency": 0.04025, ... },
  ...
];
                

// Custom view (inherits Backbone.View)
var chart = new BarChart({

  // Basic Backbone view options
  el: "#chart-container",
  collection: new Backbone.Collection(json),

  // The properties to use for rendering
  xAttr: "letter",
  yAttr: "frequency"

});

// D3 code abstracted away
chart.render();
                

// http://bl.ocks.org/mbostock/3885304

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 + ")");

d3.tsv("data.tsv", function(error, data) {

  data.forEach(function(d) {
    d.frequency = +d.frequency;
  });

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

  svg.append("g")
      .attr("class", "x axis")
      .attr("transform", "translate(0," + height + ")")
      .call(xAxis);

  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");

  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); });

});
            
var margin = {top: 20, right: 20, bottom: 30, left: 40},
    width = 960 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom;
Margins
var formatPercent = d3.format(".0%");

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

var y = d3.scale.linear()
    .range([height, 0]);
Scales
var xAxis = d3.svg.axis()
    .scale(x)
    .orient("bottom");

var yAxis = d3.svg.axis()
    .scale(y)
    .orient("left")
    .tickFormat(formatPercent);
Axes
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 + ")");
Margins
d3.tsv("data.tsv", function(error, data) {

  data.forEach(function(d) {
    d.frequency = +d.frequency;
  });
Data
  x.domain(data.map(function(d) { return d.letter; }));
  y.domain([0, d3.max(data, function(d) { return d.frequency; })]);
Scales
  svg.append("g")
      .attr("class", "x axis")
      .attr("transform", "translate(0," + height + ")")
      .call(xAxis);

  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");
Axes
  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); });
});
Bars

D3 is declarative,
MV* is object-oriented

Encapsulation

(Towards Reusable Charts)

Let's wrap D3 in Backbone

Dimensions and margin convention


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("#chart").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 ChartBase = Backbone.View.extend({

  // Default options
  defaults: {
    margin: {top: 20, right: 20, bottom: 30, left: 40}
  },

  render: function() {
    var margin = this.options.margin;
    this.width = this.$el.width() - margin.left - margin.right;
    this.height = this.$el.height() - margin.top - margin.bottom;

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

    return this;
  }

});

Base chart interface


var ChartBase = Backbone.View.extend({

  defaults: {
    xAttr: "x",
    yAttr: "y",
    margin: {...}
  },

  render: function() {
    ... // Append SVG element, set margins

    this.scales = {
        x: this.getXScale(),
        y: this.getYScale()
    };
    this.renderAxes();
    this.renderData();

    return this;
  }

});

Usage:


// Create chart object (BarChart inherits ChartBase)
var chart = new BarChart({

  // Basic Backbone view options
  el: "#chart-container",
  collection: new Backbone.Collection(json),

  // Override default options to match data
  // (use default margins)
  xAttr: "letter",
  yAttr: "frequency"

});

// Sets margins, gets scales, renders data
chart.render();

Bar chart: Scales


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

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

...

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

var BarChart = ChartBase.extend({

  defaults: _.defaults({
    barPadding: 0.1
  }, ChartBase.prototype.defaults),

  getXScale: function() {
    var padding = this.options.barPadding;
    return d3.scale.ordinal()
      .rangeRoundBands([0, this.width], padding)
      .domain(this.collection.pluck(this.options.xAttr));
  },

  getYScale: function() {
    return d3.scale.linear()
      .rangeRound([this.height, 0])
      .domain([0, d3.max(this.collection.pluck(this.options.yAttr))]);
  }

});

Bar chart: Axes


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

var yAxis = d3.svg.axis()
    .scale(y)
    .orient("left")
    .tickFormat(d3.format(".0%"));

...

svg.append("g")
    .attr("class", "x axis")
    .attr("transform", "translate(0," + height + ")")
    .call(xAxis);

svg.append("g")
    .attr("class", "y axis")
    .call(yAxis);
            

var BarChart = ChartBase.extend({

  renderAxes: function() {
    var xAxis = d3.svg.axis()
      .scale(this.scales.x)
      .orient("bottom");

    var yAxis = d3.svg.axis()
      .scale(this.scales.y)
      .orient("left")
      .tickFormat(d3.format(".0%"));

    this.svg.append("g")
      .attr("class", "x axis")
      .attr("transform", "translate(0," + this.height + ")")
      .call(xAxis);

    this.svg.append("g")
      .attr("class", "y axis")
      .call(yAxis);
  }

});

Bar chart: Rendering data


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); });
            

var BarChart = ChartBase.extend({

  renderData: function() {
    var chart = this,
        x = this.scales.x,
        y = this.scales.y;

    this.svg.selectAll(".bar")
        .data(this.mapData()) // { x: xAttr, y: yAttr }
      .enter().append("rect")
        .attr("class", "bar")
        .attr("x", function(d) { return x(d.x); })
        .attr("width", x.rangeBand())
        .attr("y", function(d) { return y(d.y); })
        .attr("height", function(d) { return chart.height - y(d.y); });
  }

});

As basic as it gets


var chart = new BarChart({

  el: "#chart-container",
  collection: new Backbone.Collection(json),

  xAttr: "letter",
  yAttr: "frequency"

});

chart.render();

But wait, there's more

Re-rendering when data changes

Using remote data (AJAX)

Interactivity (DOM events)

More chart types

Getting started

d3js.org, D3.js Gallery

backbonejs.org, tbranyen/backbone-boilerplate


Alternate approaches

bl.ocks.org/milroc/5522467

Thanks, stay tuned!

We    open source


bitdeli.com/free

jyri@bitdeli.com / @jtuulos

jtuulos.github.io/bayd3-may2013