Relative Strength Index (RSI)

Install and import

npm install fintech-algorithms

import { rsi } from "fintech-algorithms/technical-indicators/momentum/rsi";

Signature

rsi(close, p)

Relative strength index: Wilder-smoothed average gain over average loss, mapped to 0–100. In a strong trend a high reading means strength persisting, not exhaustion — which is the most common misreading of this indicator.

Parameters

Returns

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

A single parallel series, rsi.

Warm-up

The first p positions are null. Wilder smoothing seeds on the first full window of gains and losses.

Errors

• When p < 1 or is not an integer — throws RangeError

Complexity: time O(n), 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, 100.999214, 102.324548, 103.755998, 105.030823, 105.911843]

Showing 6 of 120 elements.

Call

rsi(close, p)

Returns

object with 1 field: rsi

{
  "rsi": [null, null, null, null, null, null]
}

Other exports

This module also exports stochastic, stochastic_rsi, williams_r, cci, ultimate_oscillator, tsi, connors_rsi. Every module additionally exports run as an alias of its primary function, and a meta object carrying its catalog id, domain, family, shape and article URL.

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

• New Concepts in Technical Trading Systems — J. Welles Wilder / Windsor Books
• TA-Lib Technical Analysis Documentation — TA-Lib
• Claim-role ledger
• Evidence boundary