var cartogram = function (objects_key, scale_key) {
    var margin = {top: 20, right: 20, bottom: 20, left: 20},
        width = 960,
        height = 500,
        proj = d3.geo.albers(),
        scale = d3.scale.linear(),
        zoom = d3.behavior.zoom().translate([0,300]).scale(0.7);

    function cartogram(selection) {
        selection.each(function (d) {
            var svg = d3.select(this).selectAll("svg").data([d]);
            var gEnter = svg.enter().append("svg")
                    .attr("width", width)
                    .attr("height", height);
            var path = d3.geo.path().projection(proj);

            var g = svg.append("g")
                    .attr("transform", "translate(" + zoom.translate() + ")" +
                        "scale(" + [zoom.scale(), zoom.scale()] + ")");

            var land = g.append("path")
                    .attr("class", "land")
                    .datum(topojson.object(d, d.objects[objects_key]))
                    .attr("d", path);

            var areas = g.selectAll(".area")
                    .data(topojson.object(d, d.objects[objects_key]).geometries)
                    .enter().append("path")
                    .attr("class", "area")
                    .attr("d", path)
                    .attr("transform", function (d) {
                        var centroid = path.centroid(d),
                                    x = centroid[0],
                                    y = centroid[1];
                        return "translate(" + x + "," + y + ")"
                            + "scale(" + Math.sqrt(d.properties[scale_key] * 5 || 0) + ")"
                            + "translate(" + -x + "," + -y + ")";
                    })
                    .style("stroke-width", function(d) {
                        return 1 / Math.sqrt(d.properties[scale_key] * 5 || 1);
                    });;
        });
    }

    cartogram.width = function (value) {
        if (!arguments.length) return width;
        width = value;
        return cartogram;
    };

    cartogram.height = function (value) {
        if (!arguments.length) return height;
        height = value;
        return cartogram;
    };

    cartogram.zoom = function (value) {
        if (!arguments.length) return zoom;
        zoom = value;
        return cartogram;
    };

    return cartogram;
};