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Fractal Channel — Averages & volatility, on the price chart.
What Fractal Channel measures
A high fractal at bar j requires its high to be strictly greater than the highs of the k bars on each side; a low fractal requires the symmetric condition on lows. A fractal centred at bar j is only knowable once its k right-hand bars exist, so at each bar the indicator tests only the centre j = i - k. That confirmation delay is applied deliberately: the value shown at a bar is the value a trader actually had at that bar, with no lookahead. Both edges need at least one confirmed fractal before anything is drawn.
The formula, as implemented
This is not how the indicator is usually defined elsewhere — it is what the shipped code computes, documented next to the implementation:
Fractal Channel — canal des fractales de Bill Williams. fractale HAUTE en j ⟺ high[j] > high[j±1..j±k] (strict des DEUX côtés) fractale BASSE en j ⟺ low[j] < low[j±1..j±k] CONFIRMATION : une fractale centrée en j n'est connue qu'à la barre j + k (il faut ses k barres de droite). L'indicateur respecte ce délai — à la barre i on ne teste que le centre j = i − k : AUCUN regard vers le futur, la valeur affichée à la barre i est celle qu'un trader avait à la barre i. upper[i] = high de la dernière fractale haute confirmée ≤ i (TENUE jusqu'à la suivante) lower[i] = low de la dernière fractale basse confirmée ≤ i basis[i] = milieu des deux Ce n'est donc PAS `donchian` (extrême GLISSANT de N barres, qui se met à jour à chaque nouveau plus haut) ni `price-envelopes` (enveloppe % d'une SMA) : les bornes ici sont ÉVÉNEMENTIELLES — plates entre deux pivots, et elles peuvent RESSERRER (une nouvelle fractale haute plus basse que la précédente abaisse le plafond), ce qu'un canal de Donchian ne fait jamais dans la fenêtre. Warm-up : trou synchronisé tant que les DEUX bornes n'existent pas (il faut au moins une fractale haute ET une basse confirmées). Défaut k=2 (la fractale à 5 barres de Williams).
How to read it
- The edges are the last agreed pivots, not the extremes of the recent range. They mark prices the market has already turned at.
- A flat section means no new fractal has been confirmed on that side, and the longer the flat, the older the reference level.
- This channel can tighten on its own: a new high fractal lower than the previous one pulls the ceiling down even though price made no new extreme.
- Because of the confirmation delay a level appears k bars after the pivot bar, which is two bars with the default wing.
- A touch of an edge is a return to a prior turning point; whether it holds is a question for the flow at that price, not for the channel.
Parameters and defaults
The only calculation parameter is the wing, default 2, which reproduces Williams's five-bar fractal with two bars on each side of the centre. Values from 1 to 10 are accepted. A larger wing demands a more isolated pivot, so fractals become rarer, the edges update less often, and the confirmation delay grows to match.
| Parameter | Type | Default | Range |
|---|---|---|---|
| Wing bars | number | 2 | 1 – 10 |
What it does not show
The channel is silent about everything that happens between pivots, and its levels can be old enough to have lost their relevance without the plot showing it. Strict inequality on both sides means an equal high next to the pivot cancels the fractal, so noisy or heavily rounded data can produce fewer pivots than the chart suggests. Only highs and lows are read, so a pivot formed on one thin print looks exactly like one formed on heavy two-sided trade. Nothing at all is drawn until a high and a low fractal both exist, which can take a while after a chart reload.
Related indicators
- SMA — Averages & volatility
- EMA — Averages & volatility
- WMA — Averages & volatility
- Hull MA — Averages & volatility
- ATR (Wilder) — Averages & volatility
- Bollinger — Averages & volatility
This page in other languages
Frequently asked questions
- Why does a fractal only appear two bars after the pivot?
- A fractal is defined by the bars on both sides of its centre, so the right-hand bars must exist before it can be validated. With the default wing of 2 that is a two-bar delay, and the indicator applies it instead of back-dating the level, which keeps the plotted history identical to what was visible in real time.
- Can the fractal channel get narrower?
- Yes. If a newly confirmed high fractal sits lower than the previous one, the upper edge drops to it. A Donchian channel does not behave this way, since its edge recedes only when the bar holding the extreme leaves the lookback window.
- What is a Bill Williams fractal?
- It is a pivot pattern of 2k+1 bars in which the centre bar has the highest high, or the lowest low, of the group. Williams published it with two bars on each side, which is the five-bar form used here by default.