D3 Grouped Bar Chart

HTML

<svg width="900" height="400"></svg>

JavaScript

var svg = d3.select("svg"),
            margin = { top: 20, right: 20, bottom: 30, left: 40 },
            width = +svg.attr("width") - margin.left - margin.right,
            height = +svg.attr("height") - margin.top - margin.bottom,
            g = svg.append("g").attr("transform", "translate(" + margin.left + "," + margin.top + ")");

        var x0 = d3.scaleBand()
            .rangeRound([0, width])
            .paddingInner(0.2);

        var x1 = d3.scaleBand()
            .padding(0.05);

        var y = d3.scaleLinear()
            .rangeRound([height, 0]);

       /* var z = d3.scaleOrdinal()
            .range(["#98abc5", "#8a89a6", "#7b6888", "#6b486b", "#a05d56", "#d0743c", "#ff8c00"]);*/
             var z = d3.scaleOrdinal()
            .range(["#98abc5", "#8a89a6"]);

        /*var vals = '[{"State":"CA","Under 5 Years":2704659,"5 to 13 Years":4499890,"14 to 17 Years":2159981,"18 to 24 Years":3853788,"25 to 44 Years":10604510,"45 to 64 Years":8819342,"65 Years and Over":4114496},{"State":"TX","Under 5 Years":2027307,"5 to 13 Years":3277946,"14 to 17 Years":1420518,"18 to 24 Years":2454721,"25 to 44 Years":7017731,"45 to 64 Years":5656528,"65 Years and Over":2472223},{"State":"NY","Under 5 Years":1208495,"5 to 13 Years":2141490,"14 to 17 Years":1058031,"18 to 24 Years":1999120,"25 to 44 Years":5355235,"45 to 64 Years":5120254,"65 Years and Over":2607672},{"State":"FL","Under 5 Years":1140516,"5 to 13 Years":1938695,"14 to 17 Years":925060,"18 to 24 Years":1607297,"25 to 44 Years":4782119,"45 to 64 Years":4746856,"65 Years and Over":3187797},{"State":"IL","Under 5 Years":894368,"5 to 13 Years":1558919,"14 to 17 Years":725973,"18 to 24 Years":1311479,"25 to 44 Years":3596343,"45 to 64 Years":3239173,"65 Years and Over":1575308},{"State":"PA","Under 5 Years":737462,"5 to 13 Years":1345341,"14 to 17 Years":679201,"18 to 24 Years":1203944,"25 to 44 Years":3157759,"45 to 64 Years":3414001,"65 Years and Over":1910571}]';*/
        var...