Bollinger Bands

Install and import

bash

npm install fintech-algorithms

import { bollinger_bands } from "fintech-algorithms/technical-indicators/volatility-and-channels/bollinger-bands";

Signature

bollinger_bands(close, p, multiplier)

A moving average with bands a number of standard deviations away, so the channel widens and narrows with realised volatility.

Parameters

Name	Type	Notes
`close`	`number[]`	Per-bar closing prices, chronological.
`p`	`number`	Lookback for both the average and the standard deviation. min: 1 · integer: true
`multiplier`	`number`	Number of standard deviations from the middle band to each outer band. min: 0

Returns

Record<string, (number | null)[]> · length same-as-input

Parallel series: middle, stddev, upper, lower, and percent_b — where price sits within the channel, 0 at the lower band and 1 at the upper.

Warm-up

The first p − 1 positions are null.

Errors

When p < 1, is not an integer, or multiplier is negative — throws RangeError

Complexity: time O(n × p), space O(n).

Worked example

executed Captured by running this function on the input its own test provides. Real output of real code — but not asserted against a published figure.

Input

[100, 100.54129063, 101.06589044, 101.55765885, 102.00153762, 102.3840473]

Showing 6 of 240 elements.

multiplier

Call

bollinger_bands(close, p, multiplier)

Returns

object with 5 fields: middle, stddev, upper, lower, percent_b

{
  "middle": [null, null, null, null, null, null],
  "stddev": [null, null, null, null, null, null],
  "upper": [null, null, null, null, null, null],
  "lower": [null, null, null, null, null, null],
  "percent_b": [null, null, null, null, null, null]
}

Diagrams

How it works

This page states the contract — how to call it correctly. The article explains the concept: why it works, and where it breaks.

Read the article →

References

Bollinger Bands Rules — John Bollinger
Bollinger Bands (BB) — TradingView
Bollinger Bands — TA-Lib
ta_BBANDS.c — TA-Lib
e-Handbook: Measures of Scale — NIST/SEMATECH
Public evidence boundary