function renderArc(config,first_time){

    if(first_time){
        var svg = d3.select(config.dom_element).append("svg")
        .style("width", config.width + config.margin.left + config.margin.right)
        .style("height", config.height + config.margin.top + config.margin.bottom);

        var arc = d3.svg.arc()
            .innerRadius(config.inner_radius)
            .outerRadius(config.outer_radius)
            .startAngle(toRadians(config.start_angle))
            .endAngle(toRadians(config.end_angle));

        svg.append("path")
            .attr("transform","translate(" + config.x+ "," + config.y+ ")")
            .attr("class", "arc")
            .attr("d", arc)
            .style("fill",config.fill_color)
            .style("stroke",config.stroke_color)
            .style("stroke-width",config.stroke_width)

        $("#x").val(config.x);
        $("#y").val(config.y);
        $("#startAngle").val(config.start_angle);
        $("#endAngle").val(config.end_angle);
        $("#innerRadius").val(config.inner_radius);
        $("#outerRadius").val(config.outer_radius);
        $("#width").val(config.width);
        $("#height").val(config.height);
        $("#fillColor").val(config.fill_color);
        $("#strokeColor").val(config.stroke_color);
        $("#strokeWidth").val(config.stroke_width);

    }else{
        var dom_element = d3.select("svg")
        .style("width", config.width + config.margin.left + config.margin.right)
        .style("height", config.height + config.margin.top + config.margin.bottom);

        var arc = d3.svg.arc()
            .innerRadius(config.inner_radius)
            .outerRadius(config.outer_radius)
            .startAngle(toRadians(config.start_angle))
            .endAngle(toRadians(config.end_angle));

        dom_element.select(".arc")
            .attr("transform","translate(" + config.x+ "," + config.y+ ")")
            .attr("d", arc)
            .style("fill",config.fill_color)
            .style("stroke",config.stroke_color)
            .style("stroke-width",config.stroke_width)

    }
}

    function toRadians(degs){
        return Math.PI*degs/180;
    }