function updatePolarScale(ecModel, api) {
	        var polar = this;
	        var angleAxis = polar.getAngleAxis();
	        var radiusAxis = polar.getRadiusAxis();
	        // Reset scale
	        angleAxis.scale.setExtent(Infinity, -Infinity);
	        radiusAxis.scale.setExtent(Infinity, -Infinity);

	        ecModel.eachSeries(function (seriesModel) {
	            if (seriesModel.coordinateSystem === polar) {
	                var data = seriesModel.getData();
	                radiusAxis.scale.unionExtentFromData(data, 'radius');
	                angleAxis.scale.unionExtentFromData(data, 'angle');
	            }
	        });

	        niceScaleExtent(angleAxis.scale, angleAxis.model);
	        niceScaleExtent(radiusAxis.scale, radiusAxis.model);

	        // Fix extent of category angle axis
	        if (angleAxis.type === 'category' && !angleAxis.onBand) {
	            var extent = angleAxis.getExtent();
	            var diff = 360 / angleAxis.scale.count();
	            angleAxis.inverse ? (extent[1] += diff) : (extent[1] -= diff);
	            angleAxis.setExtent(extent[0], extent[1]);
	        }
	    }
Convert a (x, y) point to (radius, angle) coord
@param {Array.<number>} point
@return {Array.<number>}