Visualize changes in Australian Federal Government department staffing levels using a Treemap

README.md

Australian Federal Budget 2014/15: Changes to Public Service Staffing Levels

A treemap is used to display the hierarchy of Federal Government ministries and departments. The size and colour of the rectangles encode the number of staff (2013/14 or 2014/15) and the change in staffing levels (absolute or percentage), respectively.

Source data comes from Budget Paper 4 Table 2.2 Average Staffing Table.

The treemap was implemented using D3.js, and borrowed heavily from a couple of excellent examples:

• Bill White's treemap with title headers
• Thomas G. Kristensen's treemap with tooltips

The source-code is available on Github and is licensed under a Creative Commons Attribution 4.0 International License.

For more information see this Vislives! blog post.

TODO

• add a colour legend
• auto-range the colour scales

asl.json

{
    "name": "Public Service",
    "children": [
        {
            "name": "Agriculture",
            "children": [
                {
                    "name": "Department of Agriculture",
                    "asl": [4258, 4397, 4165]
                },
                {
                    "name": "Australian Fisheries Management Authority",
                    "asl": [189, 185, 185]
                },
                {
                    "name": "Australian Grape and Wine Authority",
                    "asl": [0, 0, 55]
                },
                {
                    "name": "Australian Pesticides and Veterinary Medicines Authority",
                    "asl": [183, 166, 176]
                },
                {
                    "name": "Cotton Research and Development Corporation",
                    "asl": [14, 13, 14]
                },
                {
                    "name": "Fisheries Research and Development Corporation",
                    "asl": [13, 12, 13]
                },
                {
                    "name": "Grains Research and Development Corporation",
                    "asl": [61, 66, 76]
                },
                {
                    "name": "Grape and Wine Research and Development Corporation",
                    "asl": [11, 11, 0]
                },
                {
                    "name": "Rural Industries Research and Development Corporation",
                    "asl": [27, 27, 23]
                },
                {
                    "name": "Sugar Research and Development Corporation",
                    "asl": [8, 2, 0]
                },
                {
                    "name": "Wine Australia Corporation",
                    "asl": [49, 45, 0]
                }
            ]
        },
        {
            "name": "Attorney-General",
            "children": [
                {
                    "name": "Attorney-General's Department",
                    "asl": [1461, 1552, 1614]
                },
                {
                    "name": "Australia Business Arts Foundation Limited",
                    "asl": [33, 30, 18]
                },
                {
                    "name": "Australia Council",
                    "asl": [124, 128, 127]
                },
                {
                    "name": "Australian Film, Television and Radio School",
                    "asl": [150, 150, 150]
                },
                {
                    "name": "Australian National Maritime Museum",
                    "asl": [115, 113, 108]
                },
                {
                    "name": "Administrative Appeals Tribunal",
                    "asl": [170, 170, 163]
                },
                {
                    "name": "Australian Commission for Law Enforcement Integrity",
                    "asl": [34, 36, 38]
                },
                {
                    "name": "Australian Crime Commission",
                    "asl": [504, 536, 515]
                },
                {
                    "name": "Australian Federal Police",
                    "asl": [6416, 6586, 6239]
                },
                {
                    "name": "Australian Financial Security Authority",
                    "asl": [420, 450, 450]
                },
                {
                    "name": "Australian Human Rights Commission",
                    "asl": [125, 123, 142]
                },
                {
                    "name": "Australian Institute of Criminology",
                    "asl": [47, 47, 47]
                },
                {
                    "name": "Australian Law Reform Commission",
                    "asl": [16, 14, 13]
                },
                {
                    "name": "Australian Security Intelligence Organisation",
                    "asl": [1778, 1750, 1720]
                },
                {
                    "name": "Australian Transaction Reports and Analysis Centre",
                    "asl": [274, 268, 259]
                },
                {
                    "name": "Bundanon Trust",
                    "asl": [19, 19, 20]
                },
                {
                    "name": "CrimTrac Agency",
                    "asl": [228, 231, 229]
                },
                {
                    "name": "Family Court and Federal Circuit Court",
                    "asl": [789, 789, 766]
                },
                {
                    "name": "Federal Court of Australia",
                    "asl": [425, 418, 406]
                },
                {
                    "name": "High Court of Australia",
                    "asl": [82, 82, 79]
                },
                {
                    "name": "National Archives of Australia",
                    "asl": [429, 416, 412]
                },
                {
                    "name": "National Film & Sound Archive",
                    "asl": [211, 206, 178]
                },
                {
                    "name": "National Gallery of Australia",
                    "asl": [245, 257, 245]
                },
                {
                    "name": "National Library of Australia",
                    "asl": [434, 423, 412]
                },
                {
                    "name": "National Museum of Australia",
                    "asl": [221, 221, 218]
                },
                {
                    "name": "National Portrait Gallery of Australia",
                    "asl": [59, 53, 52]
                },
                {
                    "name": "Office of Parliamentary Counsel",
                    "asl": [113, 105, 99]
                },
                {
                    "name": "Office of the Australian Information Commissioner",
                    "asl": [80, 77, 39]
                },
                {
                    "name": "Office of the Director of Public Prosecutions",
                    "asl": [423, 452, 412]
                },
                {
                    "name": "Old Parliament House",
                    "asl": [72, 72, 68]
                },
                {
                    "name": "Screen Australia",
                    "asl": [112, 115, 108]
                }
            ]
        },
        {
            "name": "Communications",
            "children": [
                {
                    "name": "Department of Communications",
                    "asl": [585, 530, 430]
                },
                {
                    "name": "Australian Broadcasting Corporation",
                    "asl": [4619, 4650, 4642]
                },
                {
                    "name": "Australian Communications and Media Authority",
                    "asl": [523, 512, 468]
                },
                {
                    "name": "Special Broadcasting Service Corporation",
                    "asl": [1058, 1081, 1081]
                },
                {
                    "name": "Telecommunications Universal Service Management Agency",
                    "asl": [17, 15, 0]
                }
            ]
        },
        {
            "name": "Defence",
            "children": [
                {
                    "name": "Department of Defence – Civilian",
                    "asl": [15547, 15268, 14883]
                },
                {
                    "name": "Australian War Memorial",
                    "asl": [339, 329, 333]
                },
                {
                    "name": "Defence Housing Australia",
                    "asl": [614, 679, 673]
                },
                {
                    "name": "Defence Materiel Organisation",
                    "asl": [5670, 5243, 5209]
                },
                {
                    "name": "Department of Defence – Military",
                    "asl": [58235, 56395, 58839]
                },
                {
                    "name": "Department of Defence – Reserves",
                    "asl": [20450, 20200, 20500]
                },
                {
                    "name": "Department of Veterans' Affairs",
                    "asl": [1924, 1924, 1870]
                }
            ]
        },
        {
            "name": "Departments of the Parliament",
            "children": [
                {
                    "name": "Department of Parliamentary Services",
                    "asl": [705, 711, 708
                    ]
                },
                {
                    "name": "Department of the House of Representatives",
                    "asl": [158, 155, 154]
                },
                {
                    "name": "Department of the Senate",
                    "asl": [155, 147, 150]
                },
                {
                    "name": "Parliamentary Budget Office",
                    "asl": [39, 35, 39]
                }
            ]
        },
        {
            "name": "Education",
            "children": [
                {
                    "name": "Department of Education, Employment and Workplace Relations",
                    "asl": [3740, 779, 0]
                },
                {
                    "name": "Department of Education",
                    "asl": [0, 1417, 1823]
                },
                {
                    "name": "Australian Curriculum Assessment and Reporting Authority",
                    "asl": [118, 116, 95]
                },
                {
                    "name": "Australian Institute of Aboriginal and Torres Strait Islander Studies",
                    "asl": [118, 134, 134]
                },
                {
                    "name": "Australian Institute for Teaching and School Leadership Limited",
                    "asl": [68, 62, 62]
                },
                {
                    "name": "Australian Research Council",
                    "asl": [120, 120, 120]
                },
                {
                    "name": "Tertiary Education Quality and Standards Agency",
                    "asl": [99, 90, 74]
                }
            ]
        },
        {
            "name": "Employment",
            "children": [
                {
                    "name": "Department of Employment",
                    "asl": [0, 1627, 1716]
                },
                {
                    "name": "Asbestos Safety and Eradication Agency",
                    "asl": [0, 7, 7]
                },
                {
                    "name": "Comcare",
                    "asl": [637, 675, 674]
                },
                {
                    "name": "Fair Work Commission",
                    "asl": [353, 330, 336]
                },
                {
                    "name": "Office of the Fair Work Building Industry Inspectorate",
                    "asl": [100, 131, 155]
                },
                {
                    "name": "Office of the Fair Work Ombudsman",
                    "asl": [693, 723, 709]
                },
                {
                    "name": "Safe Work Australia",
                    "asl": [104, 101, 101]
                },
                {
                    "name": "Workplace Gender Equality Agency",
                    "asl": [33, 32, 29]
                }
            ]
        },
        {
            "name": "Environment",
            "children": [
                {
                    "name": "Department of the Environment",
                    "asl": [2151, 2177, 1993]
                },
                {
                    "name": "Bureau of Meteorology",
                    "asl": [1536, 1508, 1450]
                },
                {
                    "name": "Director of National Parks",
                    "asl": [275, 270, 275]
                },
                {
                    "name": "Climate Change Authority",
                    "asl": [35, 29, 0]
                },
                {
                    "name": "Clean Energy Regulator",
                    "asl": [360, 338, 339]
                },
                {
                    "name": "Great Barrier Reef Marine Park Authority",
                    "asl": [205, 218, 210]
                },
                {
                    "name": "Low Carbon Australia Limited",
                    "asl": [0, 0, 0]
                },
                {
                    "name": "Murray-Darling Basin Authority",
                    "asl": [295, 295, 290]
                },
                {
                    "name": "National Water Commission",
                    "asl": [40, 37, 11]
                },
                {
                    "name": "Sydney Harbour Federation Trust",
                    "asl": [57, 53, 58]
                }
            ]
        },
        {
            "name": "Finance",
            "children": [
                {
                    "name": "Department of Finance",
                    "asl": [1468, 1395, 1369]
                },
                {
                    "name": "Australian Electoral Commission",
                    "asl": [878, 1084, 858]
                },
                {
                    "name": "Commonwealth Superannuation Corporation",
                    "asl": [72, 70, 81]
                },
                {
                    "name": "ComSuper",
                    "asl": [445, 452, 410]
                },
                {
                    "name": "Future Fund Management Agency",
                    "asl": [104, 89, 120]
                }
            ]
        },
        {
            "name": "Foreign Affairs and Trade",
            "children": [
                {
                    "name": "Department of Foreign Affairs and Trade",
                    "asl": [3981, 6175, 5640]
                },
                {
                    "name": "AusAID (Australian Agency for International Development)",
                    "asl": [1982, 0, 0]
                },
                {
                    "name": "Australian Centre for International Agriculture Research",
                    "asl": [73, 70, 70]
                },
                {
                    "name": "Australian Trade Commission (Austrade)",
                    "asl": [930, 1013, 996]
                },
                {
                    "name": "Export Finance Insurance Corporation - National Interest Account",
                    "asl": [7, 5, 5]
                },
                {
                    "name": "Tourism Australia",
                    "asl": [198, 204, 204]
                }
            ]
        },
        {
            "name": "Health",
            "children": [
                {
                    "name": "Department of Health",
                    "asl": [4567, 3731, 3405]
                },
                {
                    "name": "Australian Commission on Safety and Quality in Health Care",
                    "asl": [58, 68, 77]
                },
                {
                    "name": "Australian Institute of Health and Welfare",
                    "asl": [315, 306, 294]
                },
                {
                    "name": "Australian National Preventive Health Agency",
                    "asl": [40, 33, 0]
                },
                {
                    "name": "Australian Organ and Tissue Donation and Transplantation Authority",
                    "asl": [28, 28, 28]
                },
                {
                    "name": "Australian Radiation Protection and Nuclear Safety Agency",
                    "asl": [153, 135, 130]
                },
                {
                    "name": "Australian Sports Anti-Doping Authority",
                    "asl": [74, 78, 62]
                },
                {
                    "name": "Australian Sports Commission (includes Australian Sports Foundation Limited)",
                    "asl": [696, 642, 505]
                },
                {
                    "name": "Cancer Australia",
                    "asl": [72, 66, 72]
                },
                {
                    "name": "Food Standards Australia and New Zealand",
                    "asl": [118, 115, 107]
                },
                {
                    "name": "General Practice Education and Training Limited",
                    "asl": [61, 62, 31]
                },
                {
                    "name": "Health Workforce Australia",
                    "asl": [140, 129, 0]
                },
                {
                    "name": "Independent Hospital Pricing Authority",
                    "asl": [59, 55, 59]
                },
                {
                    "name": "National Blood Authority",
                    "asl": [53, 54, 53]
                },
                {
                    "name": "National Health and Medical Research Council",
                    "asl": [217, 217, 208]
                },
                {
                    "name": "National Health Funding Body",
                    "asl": [21, 19, 19]
                },
                {
                    "name": "National Health Performance Authority",
                    "asl": [53, 53, 54]
                },
                {
                    "name": "National Mental Health Commission",
                    "asl": [13, 13, 13]
                },
                {
                    "name": "Private Health Insurance Administration Council",
                    "asl": [35, 33, 32]
                },
                {
                    "name": "Private Health Insurance Ombudsman",
                    "asl": [12, 12, 12]
                },
                {
                    "name": "Professional Services Review",
                    "asl": [23, 17, 17]
                }
            ]
        },
        {
            "name": "Immigration and Border Protection",
            "children": [
                {
                    "name": "Department of Immigration and Border Protection",
                    "asl": [9080, 9304, 8904]
                },
                {
                    "name": "Australian Customs and Border Protection Service",
                    "asl": [5000, 5000, 4920]
                },
                {
                    "name": "Migration Review Tribunal and Refugee Review Tribunal",
                    "asl": [420, 420, 420]
                }
            ]
        },
        {
            "name": "Industry",
            "children": [
                {
                    "name": "Department of Resources, Energy and Tourism",
                    "asl": [655, 0, 0]
                },
                {
                    "name": "Department of Industry",
                    "asl": [3630, 3715, 2983]
                },
                {
                    "name": "Australian Institute of Marine Science",
                    "asl": [202, 204, 202]
                },
                {
                    "name": "Australian Nuclear Science and Technology Organisation",
                    "asl": [1276, 1267, 1204]
                },
                {
                    "name": "Australian Renewable Energy Agency",
                    "asl": [2, 2, 0]
                },
                {
                    "name": "Australian Skills Quality Authority",
                    "asl": [211, 197, 197]
                },
                {
                    "name": "Commonwealth Scientific and Industrial Research Organisation",
                    "asl": [5550, 5523, 5034]
                },
                {
                    "name": "Geoscience Australia",
                    "asl": [720, 716, 620]
                },
                {
                    "name": "IP Australia",
                    "asl": [1067, 1066, 1048]
                },
                {
                    "name": "National Offshore Petroleum Safety and Environmental Management Authority",
                    "asl": [121, 111, 135]
                }
            ]
        },
        {
            "name": "Infrastructure and Regional Development",
            "children": [
                {
                    "name": "Department of Regional Australia, Local Government, Arts and Sport",
                    "asl": [482, 100, 0]
                },
                {
                    "name": "Department of Infrastructure and Regional Development",
                    "asl": [994, 1110, 1164]
                },
                {
                    "name": "Australian Maritime Safety Authority",
                    "asl": [358, 358, 367]
                },
                {
                    "name": "Australian Transport Safety Bureau",
                    "asl": [118, 110, 104]
                },
                {
                    "name": "Civil Aviation Safety Authority",
                    "asl": [855, 855, 833]
                },
                {
                    "name": "National Capital Authority",
                    "asl": [56, 54, 56]
                },
                {
                    "name": "National Transport Commission",
                    "asl": [45, 43, 40]
                }
            ]
        },
        {
            "name": "Prime Minister and Cabinet",
            "children": [
                {
                    "name": "Department of the Prime Minister and Cabinet",
                    "asl": [771, 1720, 2314]
                },
                {
                    "name": "Aboriginal Hostels Limited",
                    "asl": [445, 406, 396]
                },
                {
                    "name": "Anindilyakwa Land Council",
                    "asl": [48, 38, 21]
                },
                {
                    "name": "Australian National Audit Office",
                    "asl": [348, 349, 349]
                },
                {
                    "name": "Australian Public Service Commission",
                    "asl": [254, 248, 226]
                },
                {
                    "name": "Central Land Council",
                    "asl": [231, 231, 228]
                },
                {
                    "name": "Indigenous Business Australia",
                    "asl": [227, 232, 236]
                },
                {
                    "name": "Indigenous Land Corporation",
                    "asl": [265, 265, 265]
                },
                {
                    "name": "National Australia Day Council Limited",
                    "asl": [11, 12, 13]
                },
                {
                    "name": "Northern Land Council",
                    "asl": [329, 226, 226]
                },
                {
                    "name": "Office of National Assessments",
                    "asl": [148, 135, 130]
                },
                {
                    "name": "Office of the Commonwealth Ombudsman",
                    "asl": [136, 136, 129]
                },
                {
                    "name": "Office of the Inspector-General of Intelligence and Security",
                    "asl": [12, 12, 11]
                },
                {
                    "name": "Office of the Official Secretary to the Governor-General",
                    "asl": [86, 82, 80]
                },
                {
                    "name": "Outback Stores Pty Ltd",
                    "asl": [150, 143, 152]
                },
                {
                    "name": "Tiwi Land Council",
                    "asl": [11, 5, 5]
                },
                {
                    "name": "Torres Strait Regional Authority",
                    "asl": [139, 137, 146]
                },
                {
                    "name": "Wreck Bay Aboriginal Community Council",
                    "asl": [32, 30, 30]
                }
            ]
        },
        {
            "name": "Social Services",
            "children": [
                {
                    "name": "Department of Human Services",
                    "asl": [30707, 29989, 30150]
                },
                {
                    "name": "Department of Social Services",
                    "asl": [3278, 3467, 3305]
                },
                {
                    "name": "Australian Aged Care Quality Agency",
                    "asl": [220, 208, 236]
                },
                {
                    "name": "Australian Institute of Family Studies",
                    "asl": [81, 81, 83]
                },
                {
                    "name": "National Disability Insurance Agency",
                    "asl": [0, 489, 798]
                }
            ]
        },
        {
            "name": "Treasury",
            "children": [
                {
                    "name": "Department of the Treasury",
                    "asl": [886, 899, 884]
                },
                {
                    "name": "Australian Bureau of Statistics",
                    "asl": [2685, 2600, 2500]
                },
                {
                    "name": "Australian Competition and Consumer Commission",
                    "asl": [802, 790, 735]
                },
                {
                    "name": "Australian Office of Financial Management",
                    "asl": [45, 42, 43]
                },
                {
                    "name": "Australian Prudential Regulation Authority",
                    "asl": [609, 600, 590]
                },
                {
                    "name": "Australian Securities and Investments Commission",
                    "asl": [1834, 1782, 1573]
                },
                {
                    "name": "Australian Taxation Office",
                    "asl": [22022, 21397, 19068]
                },
                {
                    "name": "Clean Energy Finance Corporation",
                    "asl": [50, 48, 0]
                },
                {
                    "name": "Commonwealth Grants Commission",
                    "asl": [40, 40, 40]
                },
                {
                    "name": "Corporations and Markets Advisory Committee",
                    "asl": [3, 3, 3]
                },
                {
                    "name": "Inspector-General of Taxation",
                    "asl": [10, 9, 14]
                },
                {
                    "name": "National Competition Council",
                    "asl": [12, 12, 4]
                },
                {
                    "name": "Office of the Auditing and Assurance Standards Board",
                    "asl": [8, 7, 7]
                },
                {
                    "name": "Office of the Australian Accounting Standards Board",
                    "asl": [24, 23, 22]
                },
                {
                    "name": "Productivity Commission",
                    "asl": [193, 185, 170]
                },
                {
                    "name": "Royal Australian Mint",
                    "asl": [241, 241, 228]
                }
            ]
        }
    ]
}

chart.js

// Chart dimensions.
var CHART_WIDTH = 1000;
var CHART_HEIGHT = 750;

// Header.
var HEADER_HEIGHT = 20;

var TEXT_WIDTH_FACTOR = 0.15;

// Scales.
var X_SCALE = d3.scale.linear().range([0, CHART_WIDTH]);
var Y_SCALE = d3.scale.linear().range([0, CHART_HEIGHT]);
var CLR_ABS_SCALE = d3.scale.linear()
    .domain([-3740, 0, 1659])
    .range(["red", "white", "green"]);
var CLR_PCT_SCALE = d3.scale.linear()
    .domain([-100, 0, 200])
    .range(["red", "white", "green"]);

// Transition (ms).
var TRANSITION_DURATION = 500;

var node;

// Treemap layout.
var treemap = d3.layout.treemap()
    .round(false)
    .size([CHART_WIDTH, CHART_HEIGHT])
    .sticky(true)
    .value(function (d) {
        return d.asl[0];
    });

// Chart element.
var chart = d3.select("#chart")
    .append("svg:svg")
    .attr("width", CHART_WIDTH)
    .attr("height", CHART_HEIGHT)
    .append("svg:g");

var mouseMove = function (d) {
    var x = d3.event.pageX + 5;
    var y = d3.event.pageY + 5;

    d3.select("#tooltip")
        .style("left", x + "px")
        .style("top", y + "px");
    d3.select("#tooltip #heading")
        .text(d.name);
    d3.select("#tooltip #asl1314")
        .text("2013-14: " + d.asl[0]);
    d3.select("#tooltip #asl1415")
        .text("2014-15: " + d.asl[2]);
    var change = d.asl[2] - d.asl[0];
    var pct = d.asl[0] == 0 ? "∞" : (change / d.asl[0] * 100).toFixed(1) + "%";
    d3.select("#tooltip #change")
        .text("Change: " + change + " (" + pct + ")");
    d3.select("#tooltip").classed("hidden", false);
};

var mouseOut = function () {
    d3.select("#tooltip").classed("hidden", true);
};

var absChange = function (d) {
    return CLR_ABS_SCALE(d.asl[2] - d.asl[0]);
};

var pctChange = function (d) {
    return d.asl[0] == 0 ? CLR_PCT_SCALE.range()[2] : CLR_PCT_SCALE(100 * (d.asl[2] - d.asl[0]) / d.asl[0]);
};

function asl1314(d) {
    return d.asl[0];
}

function asl1415(d) {
    return d.asl[2];
}

var fillColour = absChange;

// Read data.
d3.json("asl.json", function (data) {

    var root = node = data;

    // Initial layout.
    enterTransition(root);
    zoom(node);

    // Handle change to select control.
    d3.select("select").on("change", function () {
        treemap.value(this.value == "1314" ? asl1314 : asl1415)
            .nodes(root);
        zoom(node);
    });

    d3.select("#clr").on("change", function () {
        fillColour = this.value == "abs" ? absChange : pctChange;
        zoom(node);
    });
});

function enterTransition(root) {

    // Treemap nodes.
    var nodes = treemap.nodes(root);

    // Create parent cells.
    var parents = nodes.filter(function (d) {
        return d.children;
    });
    var parentCells = chart.selectAll("g.cell.parent")
        .data(parents, function (d) {
            return "p-" + d.name;
        });

    // Parent enter transition.
    var parentEnterTransition = parentCells.enter()
        .append("g")
        .attr("class", "cell parent")
        .on("click", function (d) {
            zoom(d);
        })
        .append("svg")
        .attr("class", "clip")
        .attr("width", function (d) {
            return Math.max(0.01, d.dx);
        })
        .attr("height", HEADER_HEIGHT);

    parentEnterTransition.append("rect")
        .attr("class", "head")
        .attr("width", function (d) {
            return Math.max(0.01, d.dx);
        })
        .attr("height", HEADER_HEIGHT);

    parentEnterTransition.append('text')
        .attr("class", "label")
        .attr("transform", "translate(3, 13)")
        .attr("width", function (d) {
            return Math.max(0.01, d.dx);
        })
        .attr("height", HEADER_HEIGHT)
        .text(function (d) {
            return d.name;
        });

    // Create children cells
    var children = nodes.filter(function (d) {
        return !d.children;
    });
    var childCells = chart.selectAll("g.cell.child")
        .data(children, function (d) {
            return "c-" + d.name;
        });

    // Child enter transition.
    var childEnterTransition = childCells.enter()
        .append("g")
        .attr("class", "cell child")
        .on("click", function (d) {
            zoom(node === d.parent ? root : d.parent);
        })
        .on("mousemove", mouseMove)
        .on("mouseout", mouseOut)
        .append("svg")
        .attr("class", "clip");

    childEnterTransition.append("rect")
        .classed("background", true)
        .attr("width", function (d) {
            return Math.max(0.01, d.dx);
        })
        .attr("height", function (d) {
            return d.dy;
        })
        .style("fill", function (d) {
            return fillColour(d);
        });

    childEnterTransition.append('text')
        .attr("class", "label")
        .attr('x', function (d) {
            return d.dx / 2;
        })
        .attr('y', function (d) {
            return d.dy / 2;
        })
        .attr("dy", ".35em")
        .style("display", "none")
        .text(function (d) {
            return d.name;
        });

    // Parent transition.
    parentCells.transition()
        .duration(TRANSITION_DURATION).select(".cell")
        .attr("transform", function (d) {
            return "translate(" + d.dx + "," + d.y + ")";
        });

    // Child transition.
    childCells.transition()
        .duration(TRANSITION_DURATION).select(".cell")
        .attr("transform", function (d) {
            return "translate(" + d.x + "," + d.y + ")";
        });

    // Remove exit transition.
    parentCells.exit()
        .remove();
    childCells.exit()
        .remove();
}

function idealTextColor(bgColor) {
    var red = parseInt(bgColor.substring(1, 3), 16);
    var green = parseInt(bgColor.substring(3, 5), 16);
    var blue = parseInt(bgColor.substring(5, 7), 16);
    var bgDelta = (red * 0.299) + (green * 0.587) + (blue * 0.114);
    return ((255 - bgDelta) < 105) ? "#000000" : "#ffffff";
}

function zoom(d) {

    treemap.padding([HEADER_HEIGHT / (CHART_HEIGHT / d.dy), 0, 0, 0])
        .nodes(d);

    var kx = CHART_WIDTH / d.dx;
    var ky = CHART_HEIGHT / d.dy;
    var level = d;

    X_SCALE.domain([d.x, d.x + d.dx]);
    Y_SCALE.domain([d.y, d.y + d.dy]);

    if (node != level) {
        chart.selectAll(".cell.child .label")
            .style("display", "none");
    }

    // Define the transition.
    var transition = chart.selectAll("g.cell").transition()
        .duration(TRANSITION_DURATION)
        .attr("transform", function (d) {
            return "translate(" + X_SCALE(d.x) + "," + Y_SCALE(d.y) + ")";
        })
        .each("start", function () {
            d3.select(this).select("label")
                .style("display", "none");
        })
        .each("end", function (d, i) {
            if (!i && (level !== self.root)) {
                chart.selectAll(".cell.child")
                    .filter(function (d) {
                        return d.parent === self.node; // only get the children for selected group.
                    })
                    .select(".label")
                    .style("display", "")
                    .style("fill", function (d) {
                        return idealTextColor(fillColour(d));
                    });
            }
        });

    transition.select("text")
        .text(function(d) {
            var len = Math.round(TEXT_WIDTH_FACTOR * Math.max(0.01, (kx * d.dx)));
            return d.name.length <= len ? d.name : (d.name.substr(0, len) + "...");
        });

    transition.select(".clip")
        .attr("width", function (d) {
            return Math.max(0.01, (kx * d.dx));
        })
        .attr("height", function (d) {
            return d.children ? HEADER_HEIGHT : Math.max(0.01, (ky * d.dy));
        });


    transition.select(".child .label")
        .attr("x", function (d) {
            return kx * d.dx / 2;
        })
        .attr("y", function (d) {
            return ky * d.dy / 2;
        });

    transition.select("rect")
        .attr("width", function (d) {
            return Math.max(0.01, (kx * d.dx));
        })
        .attr("height", function (d) {
            return d.children ? HEADER_HEIGHT : Math.max(0.01, (ky * d.dy));
        })
        .style("fill", function (d) {
            return d.children ? null : fillColour(d);
        });

    node = d;

    if (d3.event) {
        d3.event.stopPropagation();
    }
}

index.html

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
    <meta http-equiv="Content-Type" content="text/html;charset=utf-8">
    <title>Australian Federal Government Budget: Public Service Staffing Levels</title>
    <script type="text/javascript" src="http://d3js.org/d3.v3.min.js"></script>
    <link href="style.css" media="screen" rel="stylesheet" type="text/css"/>
</head>
<body>
<div id="chart"></div>
<div>
    <label>Size:
        <select id="size">
            <option value="1314" selected>2013-14</option>
            <option value="1415">2014-15</option>
        </select>
    </label>
    <label>Colour:
        <select id="clr">
            <option value="abs" selected>absolute</option>
            <option value="pct">relative (%)</option>
        </select>
    </label>
</div>
<p><a rel="license" href="http://creativecommons.org/licenses/by/4.0/"><img alt="Creative Commons License"
                                                                            style="border-width:0"
                                                                            src="http://i.creativecommons.org/l/by/4.0/80x15.png"/></a>
    This work is licensed under a <a rel="license" href="http://creativecommons.org/licenses/by/4.0/">Creative Commons
        Attribution 4.0 International License</a>.</p>

<div id="tooltip" class="hidden">
    <p><strong id="heading"></strong></p>

    <p><span id="asl1314"></span></p>

    <p><span id="asl1415"></span></p>

    <p><span id="change"></span></p>
</div>
</body>
<script src="chart.js" type="text/javascript"></script>
</html>

style.css

body {
    overflow: hidden;
    margin: 0;
    font-size: 12px;
    font-family: "Helvetica Neue", Helvetica;
}

svg {
    overflow: hidden;
}

rect {
    pointer-events: all;
    cursor: pointer;
    stroke: #EEEEEE;
}

.chart {
    display: block;
    margin: auto;
}

.label {
    stroke: #000000;
    fill: #000000;
    stroke-width: 0;
    margin: 2px;
    overflow: hidden;
    text-overflow: ellipsis;
}

.parent .label {
    font-size: 12px;
    stroke: #FFFFFF;
    fill: #FFFFFF;
}

.child .label {
    font-size: 11px;
    text-anchor: middle;
}

.cell {
    font-size: 11px;
    cursor: pointer
}

.head {
    fill: #555555;
}

#tooltip {
    position: absolute;
    width: auto;
    height: auto;
    padding: 10px;
    background-color: white;
    -webkit-border-radius: 10px;
    -moz-border-radius: 10px;
    border-radius: 10px;
    -webkit-box-shadow: 4px 4px 10px rgba(0, 0, 0, 0.4);
    -moz-box-shadow: 4px 4px 10px rgba(0, 0, 0, 0.4);
    box-shadow: 4px 4px 10px rgba(0, 0, 0, 0.4);
    pointer-events: none;
}

#tooltip.hidden {
    display: none;
}

#tooltip p {
    margin: 0;
    font-family: sans-serif;
    font-size: 16px;
    line-height: 20px;
}