Roll Spread Estimator [forexobroker]

595
Roll Spread Estimator implements Roll (1984) — the bid-ask bounce induces negative serial covariance in observed returns. Spread = 2 * sqrt(-cov(r[t], r[t-1])) when cov is negative. Tight spread = liquid market = clean breakouts; wide spread = thin = breakouts to fade. Signals fire on EMA cross during a tight regime. Stacked-flag visual signature distinct from any other hero indicator.

🔶 ALGORITHM

1. r0 = close - close[1]; r1 = close[1] - close[2].
2. cov(r0, r1) = sma(r0 * r1, N) - sma(r0, N) * sma(r1, N).
3. Spread = 2 * sqrt(-cov) when cov < 0; otherwise 0.
4. Quantile q (e.g., 70th percentile) over rolling window.
5. Tight regime when spread <= q.
6. EMA cross within tight fires entries.

🔶 SIGNAL LOGIC

- Buy: tight AND close crosses EMA up AND not already long AND cooldown elapsed AND barstate.isconfirmed.
- Sell: tight AND close crosses EMA down.
- Position-lock state machine.

🔶 INPUTS

- Cov Window (default 40)
- Tight Spread Quantile (default 0.7)
- Pullback EMA Length (default 8)
- Cooldown Bars (default 4)
- Visual: dashboard, glow (3 stacked flags), spread channel, buy / sell colors

🔶 ALERTS

RSE Buy, RSE Sell, RSE Any Signal, RSE Tight Start, RSE Tight End, RSE Bounce, RSE EMA Up, RSE EMA Down, RSE Webhook JSON.

🔶 LIMITATIONS

- Roll's estimator assumes the bid-ask bounce is the dominant source of negative covariance; trend-following autocorrelation can produce positive cov, in which case the estimator is undefined and returns 0.
- Forex and equities show clear bid-ask bounces; pure spot-market crypto is less consistent.
- The stacked-flag visual uses 3 overlapping flags for a thicker appearance — visually distinct but slightly heavier draw.
- Quantile-based threshold means tight is *relative* to recent history, not absolute.

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