Inverse Fisher Transform
Install and import#
npm install fintech-algorithmsimport { inverseFisherTransform } from "fintech-algorithms/technical-indicators/momentum/inverse-fisher-transform";Signature#
inverseFisherTransform(input)Squashes a scaled one-bar close change into -1..1 with the inverse Fisher transform, which is the hyperbolic tangent of the scaled input.
Parameters#
| Name | Type | Notes |
|---|---|---|
input | TopicInput | bars is a chronological array of OHLCV rows, each with a non-empty timestamp plus finite open, high, low, close and volume. From parameters this topic reads source_scale (finite number >= 0, default 0.1), the multiplier applied to the one-bar close change before the transform. The shared momentum preamble still validates period (default 14), fast_period (default 5) and slow_period (default 34) before branching, so a bad value for any of them throws even though this topic reads none of them. |
Returns#
TopicResult
series and latest carry one key, value, equal to (exp(2y) - 1) / (exp(2y) + 1) where y is source_scale times the one-bar close change. Unlike the other momentum topics there is no null warm-up prefix.
Warm-up#
The first none positions are 0 at the first bar. The first bar has no prior close, and the missing change is treated as 0 rather than propagated, so value is 0 at index 0 and ready_at is 0 on the canonical fixture.
Errors#
- When
source_scaleis negative or not a finite number — throws Error - When
parametersis supplied but is not an object — throws Error
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#
{
"bars": [
{
"timestamp": "2024-01-02",
"basis": "synthetic-unadjusted",
"open": 100,
"high": 101.45,
"low": 98.695,
"close": 100,
"volume": 750000,
"benchmark": 200
},
{
"timestamp": "2024-01-03",
"basis": "synthetic-unadjusted",
"open": 101.49111452,
"high": 103.38381693,
"low": 100.05480022,
"close": 101.78791214,
"volume": 795117,
"benchmark": 200.56326135
},
{
"timestamp": "2024-01-04",
"basis": "synthetic-unadjusted",
"open": 102.45519048,
"high": 104.6701838,
"low": 100.91147007,
"close": 102.9549389,
"volume": 840234,
"benchmark": 201.11020913
}
],
"parameters": {}
}Call#
inverseFisherTransform(input)Returns#
object with 9 fields: topic_id, title, state, ready, ready_at, series, latest, parameters, …
{
"topic_id": "D07-F03-A20",
"title": "Inverse Fisher Transform",
"state": "calculated",
"ready": true,
"ready_at": 0,
"series": {
"value": [
0,
0.17691016466328705,
0.11617573521901128,
0.027727270131488183,
-0.04007677888344102,
-0.05619814139841276
]
},
"latest": {
"value": -0.1468007517369847
},
"parameters": {},
"diagnostics": {
"causal": true,
"input_count": 96
}
}Diagrams#
Calculation flow#
Inverse Fisher Transform calculation flow
flowchart LR
A["an ordered price or OHLC series, declared lookbacks, smoot"] --> B["Validate order, basis, and finite values"]
B --> C["Apply the selected Inverse Fisher Transform convention"]
C --> D["Emit value, readiness, and diagnostics"]
D --> E["Interpret descriptively; test outcomes separately"]
B -->|invalid or insufficient| X["Withhold output with a reason"]
Inverse Fisher Transform readiness and evidence states
stateDiagram-v2
[*] --> Waiting
Waiting --> Ready: enough valid causal observations
Waiting --> Rejected: malformed or unsupported input
Ready --> Calculated: selected formula applied
Calculated --> Interpreted: diagnostic and limitation retained
Interpreted --> Ready: next observation arrives
Rejected --> Waiting: corrected input and deterministic reset
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.
References#
- TA-Lib function groups — see linked primary or authoritative record
- TA-Lib C/C++ API — see linked primary or authoritative record
- TA-Lib maintained source — see linked primary or authoritative record
- Evidence decision
- Level 1 evidence map