如何判断Boll Band发散和收敛

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比如用30分钟图，如何取出前后的数值再进行比较

没有思路，谁人指点一下，谢谢

[Loong]

StdDev大于前值发散，小于前值收敛

'Bollinger Bands, BB'

Math:

StdDev = SQRT(SUM[(CLOSE — SMA(CLOSE, N))^2, N]/N)

https://docs.mql4.com/indicators/iStdDev

Sample:

double val=iStdDev(NULL,0,10,0,MODE_EMA,PRICE_CLOSE,0);

https://docs.mql4.com/indicators/iBands

Sample:

(iBands(NULL,0,20,2,0,PRICE_CLOSE,MODE_UPPER,0)-(iBands(NULL,0,20,2,0,PRICE_CLOSE,MODE_LOWER,0)