d3.scale = {};

function d3_scaleExtent(domain) {

var start = domain[0], stop = domain[domain.length - 1];
return start < stop ? [start, stop] : [stop, start];

}

function d3_scaleRange(scale) {

return scale.rangeExtent ? scale.rangeExtent() : d3_scaleExtent(scale.range());

}