excludeElasticZero (excludeZero) {
        if (!arguments.length) {
            return this._excludeElasticZero;
        }
        this._excludeElasticZero = excludeZero;
        return this;
    }
Should the chart exclude zero when calculating elastic bubble radius?
@memberof BubbleMixin
@instance
@param  {Boolean} [excludeZero=true]
@returns {Boolean|BubbleMixin}