function RadiusAxis(scale, radiusExtent) {

    Axis.call(this, 'radius', scale, radiusExtent);

    /**
     * Axis type
     *  - 'category'
     *  - 'value'
     *  - 'time'
     *  - 'log'
     * @type {string}
     */
    this.type = 'category';
}
Get axes by type of scale
@param {string} scaleType
@return {module:echarts/coord/polar/AngleAxis|module:echarts/coord/polar/RadiusAxis}