Zoom to Group of Countries

Improved version: Zoom to Group of Countries II.

<!DOCTYPE html>
<meta charset="utf-8">
<style>
    * {
        line-height: 1;
        font-family: Arial, Helvetica, sans-serif;
        color: #999;
        margin: 0;
        padding: 0;
        text-align: center;
    }

canvas {
        border-bottom: 1px solid #dedede;
    }
</style>
<body>
<script src="//cdnjs.cloudflare.com/ajax/libs/d3/3.5.6/d3.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/topojson/1.6.19/topojson.min.js"></script>
<script src="utils.js"></script>
<script>
    var width = 960;
    var height = 480;
    var canvasScale = ((document.body.clientWidth > width) ? document.body.clientWidth : width) / width;

width *= canvasScale;
    height *= canvasScale;

var maxScale = 5;
    var scaleMargin = (40 * canvasScale / width);
    var maxCountry = (48 * canvasScale / width);

var config = {
        duration: 800,
        interval: 1050,
        fontSize: 10,
        fontShift: 2,
        font: 'Arial, Helvetica, sans-serif',
        land: {
            fillStyle: '#bbb',
            shadowColor: '#000',
            shadowOffsetY: 1,
            shadowBlur: 1
        },
        border: {
            lineWidth: 0.75,
            strokeStyle: '#fff',
            shadowColor: '#eee',
            shadowOffsetY: -1
        },
        past: {
            fillStyle: '#9c8f8f',
            shadowColor: '#fff',
            shadowOffsetY: -1,
            shadowBlur: 0
        },
        names: {
            shadowOffsetY: 0,
            fillStyle: '#fff',
            shadowColor: 'rgba(0,0,0,0.67)',
            strokeStyle: '#888'
        },
        namesBlur: {
            shadowBlur: 6,
            lineWidth: 0.5
        },
        graticule: {
            strokeStyle: '#aaa',
            lineWidth: 0.25
        }
    };

var centroidsShifts = {
        USA: [30, 10],
        IRN: [0, 5],
        FRA: [15, -12],
        IND: [-2, 8],
        MAR: [0, -6],
        CAN: [-22, 7],
        IRQ: [2, 2],
        SYR: [0, -2]
    };

var rusUsaShift = 12;
    var valueInterpolation = d3.interpolate('#ff9f9f', '#f80000');

var canvas = d3.select('body').append('canvas').attr('width', width).attr('height', height);
    var info = d3.select('body').append('div');
    var ctx = canvas.node().getContext('2d');
    var projection = d3.geo.equirectangular().translate([width / 2, height / 2]).scale(153 * canvasScale).rotate([-rusUsaShift, 0, 0]);
    var path = d3.geo.path().projection(projection).context(ctx);
    var graticule = d3.geo.graticule().step([10, 10]).extent([[-180, -90.001], [180, 90.001]])();
    var currentScale = 1;
    var currentTranslate = [0, 0];
    var pastCountries = {};
    var currentEventIndex = -1;
    var loadedEvents;
    var land, borders, countries = {};

d3.json('/darosh/raw/2d12a584a14910032ab8/countries.json', function (world) {
        initWorld(world);

d3.json('events.json', function (events) {
            loadedEvents = events;
            update();
        });
    });

function update() {
        var e = loadedEvents[currentEventIndex];

if (e) {
            var d = new Date(e[0]);
            var mm = getValuesMinMax(e[1]);

info.text('Month: ' + (d.getMonth() + 1) + '/' + d.getFullYear() +
                    ', Record: ' + (currentEventIndex + 1) + ' of ' + loadedEvents.length +
                    ', Countries: ' + Object.keys(e[1]).length +
                    ', Past countries: ' + Object.keys(pastCountries).length +
                    ', Min: ' + mm.min + ', Max: ' + mm.max + ', Sum: ' + mm.sum);

transition(e[1]);
        } else {
            transition({});
        }

currentEventIndex++;

if (currentEventIndex < loadedEvents.length) {
            setTimeout(update, config.interval);
        } else {
            transition({});
        }
    }

function initWorld(world) {
        land = topojson.merge(world, world.objects.countries.geometries);

borders = topojson.mesh(world, world.objects.countries, function (a, b) {
            return a !== b;
        });

topojson.feature(world, world.objects.countries).features.forEach(function (v) {
            countries[v.id] = v;
        });
    }

function transition(values) {
        var selectedFeatures = Object.keys(values).map(function (v) {
            return countries[v];
        });

d3.transition()
                .duration(config.duration)
                .tween('tween', function getTween() {
                    var currentRotation = projection.rotate();
                    var targetRotation = !values['RUS'] && values['USA'] ? [+rusUsaShift, 0] : [-rusUsaShift, 0];
                    var rotationInterpolation = d3.interpolate(currentRotation, targetRotation, 'easeIn');

projection.rotate(targetRotation);

var bound = groupBounds(path, selectedFeatures, width, height, maxCountry * width, maxCountry * height);
                    var size = [bound[1][0] - bound[0][0], bound[1][1] - bound[0][1]];
                    var targetScale = getScale(size, width, height, scaleMargin, maxScale);
                    var scaleInterpolation = d3.interpolate(currentScale, targetScale, 'easeIn');
                    var targetCenter = [(bound[0][0] + bound[1][0]) / 2, (bound[0][1] + bound[1][1]) / 2];
                    var realCenter = [width / 2, height / 2];

var scaledBox = [
                        [targetCenter[0] - realCenter[0] / targetScale,
                            targetCenter[1] - realCenter[1] / targetScale],
                        [targetCenter[0] + realCenter[0] / targetScale,
                            targetCenter[1] + realCenter[1] / targetScale]];

scaledBox[0][1] = scaledBox[0][1] < 0 ? 0 : scaledBox[0][1];

var targetTranslate = [-scaledBox[0][0] * targetScale, -scaledBox[0][1] * targetScale];
                    var translateInterpolation = d3.interpolate(currentTranslate, targetTranslate, 'easeIn');
                    var minMax = getValuesMinMax(values);

return function drawTween(t) {
                        // Clear
                        ctx.setTransform(1, 0, 0, 1, 0, 0);
                        ctx.clearRect(0, 0, width, height);

// Transform
                        projection.rotate(rotationInterpolation(t));
                        currentTranslate = translateInterpolation(t);
                        ctx.translate(currentTranslate[0], currentTranslate[1]);
                        currentScale = scaleInterpolation(t);
                        ctx.scale(currentScale, currentScale);

// Graticule
                        ctx.beginPath();
                        setContextSyle(ctx, config.graticule);
                        ctx.lineWidth = config.graticule.lineWidth / currentScale;
                        path(graticule);
                        ctx.stroke();

// Land
                        ctx.beginPath();
                        setContextSyle(ctx, config.land);
                        path(land);
                        ctx.fill();

// Past
                        ctx.beginPath();
                        setContextSyle(ctx, config.past);
                        Object.keys(pastCountries).forEach(function fillPast(id) {
                            if (!values[id]) {
                                path(countries[id]);
                            }
                        });
                        ctx.fill();

// Current
                        selectedFeatures.forEach(function fillNow(f) {
                            ctx.beginPath();
                            ctx.fillStyle = valueInterpolation(normalize(values[f.id], minMax));
                            path(f);
                            ctx.fill();
                            pastCountries[f.id] = true;
                        });

// Borders
                        ctx.beginPath();
                        setContextSyle(ctx, config.border);
                        ctx.lineWidth = config.border.lineWidth / currentScale;
                        path(borders);
                        ctx.stroke();

// Names
                        setContextSyle(ctx, config.names);
                        ctx.font = config.fontSize + 'px ' + config.font;
                        ctx.textAlign = 'center';
                        selectedFeatures.forEach(function addCountryName(f) {
                            var x = path.centroid(f);
                            var name = (f.properties.name).split(',')[0];

if (centroidsShifts[f.id]) {
                                x[0] += centroidsShifts[f.id][0];
                                x[1] += centroidsShifts[f.id][1];
                            }

ctx.shadowBlur = config.namesBlur.shadowBlur;
                            ctx.lineWidth = config.namesBlur.lineWidth;
                            ctx.strokeText(name, x[0], x[1] + config.fontShift);
                            ctx.shadowBlur = 0;
                            ctx.lineWidth = 0;
                            ctx.fillText(name, x[0], x[1] + config.fontShift);
                        });
                    };
                })
                .transition();
    }
</script>

https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.6/d3.min.js

https://cdnjs.cloudflare.com/ajax/libs/topojson/1.6.19/topojson.min.js