Bollinger Band data series - something is off

[szayedoud]

Hi -

I am using ib_insync with ta, and I reinstantiate my BollingerBand object after each new bar, with the last 20 bars (maybe that's the problem). BollingerBands(close=self.bars["close"], window=20, window_dev=2, fillna=True)

• When I look at what I get back from bollinger_wband() method, only the last width is accurate, the other values preceding it are all wrong

• Using the bollinger_hband() - I only get a value on the last series (most recent) and NaN for the previous 19

Any ideas on these 2 issues? I apologize in advance if I'm not using the API properly. Is there a more event driven way, where I only have to instantiate it once, and each bar is updated on current instance of the indicator ?

[szayedoud]

The dataset needs to exceeed the window size to get proper calculations.