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 (typically close) |
period |
int | MA and stdev period |
num_stdev |
float | Number of standard deviations |
Formula
BB Lower = MA(source, period) - num_stdev * stdev(source, period)Examples
close < bb_lower(close, 20, 2); // Price breakdown below lower 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_lower(close, 20, 2.0), 3) == true;Returns
float
Range
period is bound by matype's MA family (2-210 ema, 2-105 wilder) or the 2-400 windowed range for the default sma/wma, whichever is tighter, since the same period also sizes stdev()
Notes
Prices touching/exceeding the lower band may indicate oversold; wider bands (higher num_stdev) are more conservative signals