True Strength Index (TSI)

Install and import

bash

npm install fintech-algorithms

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

Signature

tsi(close, g, s)

True strength index: price change smoothed twice, divided by absolute price change smoothed the same way. The double smoothing is what separates it from a plain momentum reading.

Parameters

Name	Type	Notes
`close`	`number[]`	Per-bar closing prices, chronological.
`g`	`number`	Long smoothing span, applied first. min: 1 · integer: true
`s`	`number`	Short smoothing span, applied to the result of the first pass. min: 1 · integer: true

Returns

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

A single parallel series, tsi.

Warm-up

The first g + s − 2 positions are null. Both smoothing passes must fill.

Errors

When either span is < 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

tsi(close, g, s)

Returns

object with 1 field: tsi

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

Other exports

This module also exports rsi, stochastic, stochastic_rsi, williams_r, cci, ultimate_oscillator, 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

True Strength Index (TSI) — tsi mechanism

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

True Strength Index (TSI) — TA-Lib
Momentum, Direction, and Divergence — William Blau / Wiley
TA-Lib Technical Analysis Documentation — TA-Lib
Claim-role ledger
Evidence boundary