minRadius (radius) {
        if (!arguments.length) {
            return this.MIN_RADIUS;
        }
        this.MIN_RADIUS = radius;
        return this;
    }
Get or set the minimum radius. This will be used to initialize the radius scale's range.
@memberof BubbleMixin
@instance
@param {Number} [radius=10]
@returns {Number|BubbleMixin}