gauge = {
d3.select("svg").selectAll(".arc")
.data( ddd, function(d){ return d.id })
.enter()
.append("g")
.attr("transform",function(d){ return "translate("+ [d.x,d.y] +")" })
.attr("class","arc")
.append("path")
.attr("d", arc)
.attr("stroke", function(d) { return d3.hsl( startAngle * 20 ,1,0.5) ;} )
.attr("fill", function(d) { return d3.hsl( startAngle * 60 ,1,0.5) ;} )
d3.select("svg").selectAll(".arc").selectAll("path")
.attr("d",arc)
.attr("stroke", function(d) { return d3.hsl( startAngle * 20 ,1,0.5) ;} )
.attr("fill", function(d) { return d3.hsl( startAngle * 60 ,1,0.5) ;} )
d3.select("svg").selectAll(".arc").exit().remove();
}