bb_lower
Bollinger Bands Lower Band (MA - num_stdev * stdev)
bb_lower(source, period, num_stdev, matype="sma")
Parameters
| Name | Type | Description |
|---|---|---|
source |
field | Data series |
period |
int | MA and stdev period (commonly 20) |
num_stdev |
float | Standard deviations (commonly 2.0) |
matype |
str, optional | MA type ["sma", "ema", "wma", "wilder"], default "sma" |
Formula
```
Lower = MA - (num_stdev * STDEV)
```Examples
close < bb_lower(close, 20, 2); // Price breakdown below upper band
/* price pierced below lower band (2.5 deviations), but closed above */
low < bb_lower(close, 20, 2.5) and close > bb_lower(close, 20, 2.5);
/* lower bollinger band falling (expanding volatility) for 3 consecutive bars */
falling(bb_lower(close, 20, 2.0), 3) == true;
/* lower bollinger band rising (contracting volatility) for 3 consecutive bars */
rising(bb_upper(close, 20, 2.0), 3) == true;Returns
Float (lower band value) ## See Also bb_upper, bb_width ## Notes - Prices touching/exceeding lower band may indicate oversold - Wider bands (higher num_stdev) = more conservative signals - Can use different MA types for various smoothing characteristics