布林带指标,突破上轨超买,跌破下轨超卖,中轨为趋势
BOLL:MA(CLOSE,20); UB:BOLL+2*STD(CLOSE,20); LB:BOLL-2*STD(CLOSE,20); 强势突破:CROSS(CLOSE,UB); 弱势跌破:CROSS(LB,CLOSE);