只在布林带中轨线上方购买

//@version=4
study("Bollinger Bands 中轨线购买", overlay=true)

//中轨线
mband = sma(close, 20)

//上轨线和下轨线
upper = mband + 2 * stdev(close, 20)
lower = mband - 2 * stdev(close, 20)

//只在中轨线上方买入
buy_above = close > mband

// 绘制布林带
plot(mband, color=color.blue, linewidth=1)
plot(upper, color=color.red, linestyle=hline.style_dashed)
plot(lower, color=color.red, linestyle=hline.style_dashed)

// 绘制交易信号
plotshape(series=buy_above ? close : na, style=shape.triangleup, location=location.belowbar, color=color.green, size=size.small, text="Buy")