Donchian Predictive Channel (Zeiierman)

█ Overview
Donchian Predictive Channel (Zeiierman) extends the classic Donchian framework into a predictive structure. It does not just track where the range has been; it projects where the Donchian mid, high, and low boundaries are statistically likely to move based on recent directional bias and volatility regime.

By quantifying the linear drift of the Donchian midline and the expansion or compression rate of the Donchian range, the indicator generates a forward propagation cone that reflects the prevailing trend and volatility state. This produces a cleaner, more analytically grounded projection of future price corridors, and it remains fully aligned with the signal precision of the underlying Donchian logic.

█ How It Works

⚪ Donchian Core
The script first computes a standard Donchian Channel over a configurable Length:

• Upper Band (dcHi) – highest high over the lookback.
  
• Lower Band (dcLo) – lowest low over the lookback.
  
• Midline (dcMd) – simple midpoint of upper and lower: (dcHi + dcLo)/ 2.
  

f_getDonchian(length) =>
    hi = ta.highest(high, length)
    lo = ta.lowest(low, length)
    md = (hi + lo) * 0.5
    [hi, md, lo]
[dcHi, dcMd, dcLo] = f_getDonchian(lenDC)

⚪ Slope Estimation & Range Dynamics
To turn the Donchian Channel into a predictive model, the script measures how both the midline and the range are changing over time:

• Midline Slope (mSl) – derived from a 1-bar difference in linear regression of the midline.
  
• Range Slope (rSl) – derived from a 1-bar difference in linear regression of the Donchian range (dcHi − dcLo).
  

This pair describes both directional drift (uptrend vs. downtrend) and range expansion/compression (volatility regime).

f_getSlopes(midLine, rngVal, length) =>
    mSl = ta.linreg(midLine, length, 0) - ta.linreg(midLine, length, 1)
    rSl = ta.linreg(rngVal,   length, 0) - ta.linreg(rngVal,   length, 1)
    [mSl, rSl]

⚪ Forward Projection Engine
At the last bar, the indicator constructs a set of forward points for the mid, upper, and lower projections over Forecast Bars:

• The midline is projected linearly using the midline slope per bar.
  
• The range is adjusted using the range slope per bar, creating either a widening cone (expansion) or a tightening cone (compression).
  

Upper and lower projections are then anchored around the projected midline, with logic that keeps the structure consistent and prevents pathological flips when slope changes sign.

f_generatePoints(hi0, md0, lo0, steps, midSlp, rngSlp) =>
    upPts = array.new<chart.point>()
    mdPts = array.new<chart.point>()
    dnPts = array.new<chart.point>()
    fillPts = array.new<chart.point>()

    hi_vals = array.new_float()
    md_vals = array.new_float()
    lo_vals = array.new_float()

    curHiLocal  = hi0
    curLoLocal  = lo0
    curMidLocal = md0

    segBars = math.floor(steps / 3)
    segBars := segBars < 1 ? 1 : segBars

    for b = 0 to steps
        mdProj = md0 + midSlp * b

        prevRange = curHiLocal - curLoLocal
        rngProj   = prevRange + rngSlp * b

        hiTemp = 0.0
        loTemp = 0.0

        if midSlp >= 0
            hiTemp := math.max(curHiLocal, mdProj + rngProj * 0.5)
            loTemp := math.max(curLoLocal, mdProj - rngProj * 0.5)
        else
            hiTemp := math.min(curHiLocal, mdProj + rngProj * 0.5)
            loTemp := math.min(curLoLocal, mdProj - rngProj * 0.5)

        hiProj = hiTemp < mdProj ? curHiLocal : hiTemp
        loProj = loTemp > mdProj ? curLoLocal : loTemp

        if b % segBars == 0
            curHiLocal  := hiProj
            curLoLocal  := loProj
            curMidLocal := mdProj

        array.push(hi_vals, curHiLocal)
        array.push(md_vals, curMidLocal)
        array.push(lo_vals, curLoLocal)

        array.push(upPts, chart.point.from_index(bar_index + b, curHiLocal))
        array.push(mdPts, chart.point.from_index(bar_index + b, curMidLocal))
        array.push(dnPts, chart.point.from_index(bar_index + b, curLoLocal))
    ptSet.new(upPts, mdPts, dnPts)

⚪ Rejection Signals
The script also tracks failed Donchian breakouts and marks them as potential reversal/reversion cues:

• Signal Down: Triggered when price makes an attempt above the upper Donchian band but then pulls back inside and closes above the midline, provided enough bars have passed since the last signal.
  
• Signal Up: Triggered when price makes an attempt below the lower Donchian band but then snaps back inside and closes below the midline, also requiring sufficient spacing from the previous signal.
  

// Base signal conditions (unfiltered)
bearCond = high < dcHi and high[1] >= dcHi[1] and close > dcMd and bar_index - lastMarker >= lenDC
bullCond = low  > dcLo and low[1]  <= dcLo[1] and close < dcMd and bar_index - lastMarker >= lenDC

// Apply MA filter if enabled
if signalfilter
    bearCond := bearCond and close < ma   // Bearish only below MA
    bullCond := bullCond and close > ma   // Bullish only above MA

signalUp := false
signalDn := false

if bearCond
    lastMarker := bar_index
    signalDn   := true

if bullCond
    lastMarker := bar_index
    signalUp   := true

█ How to Use

The Donchian Predictive Channel is designed to outline possible future price trajectories. Treat it as a directional guide, not a fixed prediction tool.

⚪ Map Future Support & Resistance
Use the projected upper and lower paths as dynamic future reference levels:

• Projected upper band ≈ is likely a resistance corridor if the current trend and volatility persist.
  
• Projected lower band ≈ likely support corridor or expected downside range.
  

⚪ Trend Path & Volatility Cone
Because the projection is driven by midline and range slopes, the channel behaves like a trend + volatility cone:

• Steep positive midline slope + expanding range → accelerating, high-volatility trend.
  
• Flat midline + compressing range → coiling/contracting regime ahead of potential expansion.
  

This helps you distinguish between a gentle drift and an aggressive move that likely needs more risk buffer.


⚪ Reversion & Rejection Signals
The Donchian-based signals are especially useful for mean-reversion and fade-style trades.

• A Signal Down near the upper band can mark a failed breakout and a potential rotation back toward the midline or the lower projected band.
  
• A Signal Up near the lower band can flag a failed breakdown and a potential snap-back up the channel.
  

When Filter Signals is enabled, these signals are only generated when they align with the chart’s directional bias as defined by the moving average. Bullish signals are allowed only when the price is above the MA, and bearish signals only when the price is below it.

This reduces noise and helps ensure that reversions occur in harmony with the prevailing trend environment.


█ Settings

• Length – Donchian lookback length. Higher values produce a smoother channel with fewer but more stable signals. Lower values make the channel more reactive and increase sensitivity at the cost of more noise.
  
• Forecast Bars – Number of bars used for projecting the Donchian channel forward.
  
• Higher values create a broader, longer-term projection. Lower values focus on short-horizon price path scenarios.
  
• Filter Signals – Enables directional filtering of Donchian signals using the selected moving average. When ON, bullish signals only trigger when the price is above the MA, and bearish signals only trigger when the price is below it. This helps reduce noise and aligns reversions with the broader trend context.
  
• Moving Average Type – The type of moving average used for signal filtering and optional plotting.
  
• Choose between SMA, EMA, WMA, or HMA depending on desired responsiveness. Faster averages (EMA, HMA) react quickly, while slower ones (SMA, WMA) smooth out short-term noise.
  
• Moving Average Length – Lookback length of the moving average. Higher values create a slower, more stable trend filter. Lower values track price more tightly and can flip the directional bias more frequently.
  

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