ta.nviNegative Volume Index

//@version=6
indicator("Negative Volume Index")

plot(ta.nvi, color=color.yellow)

// the same on pine
f_nvi() =>
    float ta_nvi = 1.0
    float prevNvi = (nz(ta_nvi[1], 0.0) == 0.0) ? 1.0 : ta_nvi[1]
    if nz(close, 0.0) == 0.0 or nz(close[1], 0.0) == 0.0
        ta_nvi := prevNvi
    else
        ta_nvi := (volume < nz(volume[1], 0.0)) ? prevNvi + ((close - close[1]) / close[1]) * prevNvi : prevNvi
    result = ta_nvi

plot(f_nvi())