bb_width
Bollinger Bands Width (upper_band - lower_band)
bb_width(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
```
BB_Width = BB_Upper - BB_Lower
= 2 * num_stdev * STDEV(field, period)
```Examples
/* narrower bands (lower volatility) than 20 bars ago */
bb_width(close, 20, 2) < bb_width(close, 20, 2)[20];
/* wider bands (higher volatility) than 20 bars ago */
bb_width(close, 20, 2) > bb_width(close, 20, 2)[20];
/* increasing width (expanding volatility) for 3 consecutive bars */
rising(bb_width(close, 20, 2), 3) == true;
/* decreasing width (contracting volatility) for 3 consecutive bars */
falling(bb_width(close, 20, 2), 3) == true;Returns
Float (band width) ## See Also bb_upper, bb_lower