public boolean equals(Object obj) {
        if (obj == this) {
            return true;
        }
        if (!(obj instanceof Outlier)) {
            return false;
        }
        Outlier that = (Outlier) obj;
        if (!this.point.equals(that.point)) {
            return false;
        }
        if (this.radius != that.radius) {
            return false;
        }
        return true;