Inverse Chebyshev Filter

//@version=5
indicator("Inverse Chebyshev Filter", overlay=false)

// Input parameters
length = input(10, "Length")
order = input(3, "Order")

// Function to calculate inverse Chebyshev
invChebyshev(src, len, ord) =>
    a = math.pow(2 / (len + 1), 2)
    b = 2 * math.cos(ord * math.acos(-1) / len)
    c1 = (1 - math.sqrt(math.abs(1 - math.pow(b, 2)))) / b
    c2 = (1 - math.sqrt(math.abs(1 - math.pow(b, 2)))) / a
    c3 = -1 * c1
    c4 = -2 * c2
    res = 0.0
    res := c1 * src + c2 * nz(src[1]) + c3 * nz(res[1]) + c4 * nz(res[2])
    res

// Calculate inverse Chebyshev
invCheby = invChebyshev(close, length, order)

// Plotting
plot(invCheby, color=color.rgb(181, 115, 228), title="Inverse Chebyshev")