HMA w projection

gistfile1.txt

//@version=6
// Note: no timeframe/timeframe_gaps args — Pine forbids them in scripts that create
// drawings (our projection polyline). Use the chart's timeframe.
indicator(title="Hull Moving Average (Flat-Price Projection)", shorttitle="HMA+P", overlay=true)

length   = input.int(9, "Length", minval = 2)
src      = input(close, "Source")
projBars = input.int(20, "Projection bars", minval = 1, maxval = 500)
hmaCol   = input.color(#2196F3, "Color")   // #2196F3 = TradingView's default plot blue

// ── Historical HMA: byte-for-byte the same math as the original ──────────────
halfLen  = length / 2                       // int division, exactly as ta.wma(src, length/2)
sqrtLen  = math.floor(math.sqrt(length))

raw    = 2 * ta.wma(src, halfLen) - ta.wma(src, length)
hullma = ta.wma(raw, sqrtLen)

plot(hullma, "HMA", color = hmaCol)         // unchanged historical values

// ── Projection: recompute the HMA at future offsets k = 1..projBars,
//    assuming every future bar closes at the current price (flat) ────────────
var polyline projLine = na

if barstate.islast and not na(hullma)
    polyline.delete(projLine)

    flat = src                                          // assumed constant future price

    // Future values of raw = 2*WMA(half) - WMA(full) under the flat assumption.
    // futRaw index (k-1) holds raw at future offset k.
    futRaw = array.new_float()
    for k = 1 to projBars
        numH = 0.0
        for i = 0 to halfLen - 1
            numH += (halfLen - i) * (i < k ? flat : src[i - k])
        wmaH = numH / (halfLen * (halfLen + 1) / 2)
        numF = 0.0
        for i = 0 to length - 1
            numF += (length - i) * (i < k ? flat : src[i - k])
        wmaF = numF / (length * (length + 1) / 2)
        futRaw.push(2 * wmaH - wmaF)

    // Final smoothing: WMA(sqrtLen) over the raw series, spanning the
    // boundary between historical raw[] and future futRaw values.
    pts = array.new<chart.point>()
    pts.push(chart.point.from_index(bar_index, hullma)) // anchor at current HMA → continuous join
    for k = 1 to projBars
        num = 0.0
        for i = 0 to sqrtLen - 1
            m = k - i
            v = m >= 1 ? futRaw.get(m - 1) : raw[-m]
            num += (sqrtLen - i) * v
        pts.push(chart.point.from_index(bar_index + k, num / (sqrtLen * (sqrtLen + 1) / 2)))

    projLine := polyline.new(pts, line_color = hmaCol, line_style = line.style_dashed, line_width = 1)