function pieChart() {

    var width = 400;
    var height = 300;

    var margin = {
        top: 80,
        bottom: 80,
        left: 120,
        right: 120,
    };

    var columns = [];

    var svg;

    var pformat = d3.format('.1%');

    var colourScale = d3.scaleOrdinal()
        .domain(['N/A', 'Disagree', 'Neither Agree nor Disagree', 'Agree'])
        .range(["#222", "hsla(0, 60%, 50%, 1)", "hsla(45, 70%, 60%, 1)", "hsla(90, 50%, 50%, 1)"]);

    var pie = d3.pie()
        .sort(null)
        .value(function(d) {
            return d.value;
        });

    var key = function(d) {
        return d.data.key;
    }

    function midAngle(d) {
        return d.startAngle + (d.endAngle - d.startAngle) / 2;
    }

    function chart(selection) {
        selection.each(function(data) {

            //draw the pie chart
            svg = d3.select(this)
                .append("svg")
                .attr("width", width)
                .attr("height", height)
                .append("g")
                .attr("transform", "translate(" + margin.left + "," + margin.top + ")")

            width = width - margin.left - margin.right;
            height = height - margin.top - margin.bottom;

            svg = svg
                .append("g")
                .attr("transform", "translate(" + width / 2 + "," + height / 2 + ")");

            svg.append("g")
                .attr("class", "slices");

            svg.append("g")
                .attr("class", "labels");

            svg.append("g")
                .attr("class", "lines");

            pie_data = [];
            columns.forEach(function(c) {
                if (+data[c] > 0) {
                    pie_data.push({
                        key: c,
                        value: +data[c]
                    });
                }
            });

            var radius = Math.min(width, height) / 2;

            var arc = d3.arc()
                .outerRadius(radius * 0.6)
                .innerRadius(radius * 0.1)
                .padAngle(.02)
                .padRadius(100)
                .cornerRadius(2);

            var labelArc = d3.arc()
                .outerRadius(radius * 0.4)
                .innerRadius(radius);

            var slice = svg.select(".slices")
                .selectAll("path.slice")
                .data(pie(pie_data), key);

            slice
                .enter()
                .insert("path")
                .attr("d", arc)
                .attr("class", "slice")
                .style("stroke", "black")
                .style("stroke-width", "0.5px")
                .style("fill", function(d) {
                    return colourScale(d.data.key);
                });

            var text = svg.select(".labels")
                .selectAll("text")
                .data(pie(pie_data), key);

            text
                .enter()
                .append("text")
                .attr('class', 'label')
                .attr('id', function(d, j) {
                    return 'l-' + j;
                })
                .attr("transform", function(d) {
                    var pos = labelArc.centroid(d);
                    pos[0] = radius * (midAngle(d) < Math.PI ? 1 : -1);
                    return "translate(" + pos + ")";
                })
                .style("text-anchor", function(d) {
                    return midAngle(d) < Math.PI ? "start" : "end";
                })
                .attr("dy", ".35em")
                .attr("dx", ".35em")
                .attr("fill", "#111")
                .text(function(d) {
                    return d.data.key + " (" + pformat(d.data.value) + ")";
                })
                .call(wrap, margin.right - 20);

            arrangeLabels(svg, ".label");

            var polyline = svg.select(".lines")
                .selectAll("polyline")
                .data(pie(pie_data), key);

            polyline.enter()
                .append("polyline")
                .attr("points", function(d, j) {
                    var offset = midAngle(d) < Math.PI ? 0 : 10;
                    var label = d3.select('#l-' + j);
                    var transform = getTransformation(label.attr("transform"));
                    var pos = labelArc.centroid(d);
                    pos[0] = transform.translateX + offset;
                    pos[1] = transform.translateY;
                    var mid = labelArc.centroid(d);
                    mid[1] = transform.translateY;
                    return [arc.centroid(d), mid, pos];
                });
        })
    }

    chart.margin = function(_) {
        if (!arguments.length) return margin;
        margin = _;
        return chart;
    };

    chart.width = function(_) {
        if (!arguments.length) return width;
        width = _;
        return chart;
    };

    chart.height = function(_) {
        if (!arguments.length) return height;
        height = _;
        return chart;
    };

    chart.columns = function(_) {
        if (!arguments.length) return columns;
        columns = _;
        return chart;
    };

    return chart;
}