Average Directional Index (ADX)

// ADX indicator
//
// Input configuration
// - adxLengthInput: 14 days; how many periods are used when calculating the TR, +DM, and -DM
// - adxSmoothingLengthInput: 14 days; how many DX values are smoothed to create the ADX line
//
// Output:
// - RSI solid line
// - Overbought dotted line
// - Oversold dotted line

//@version=5
indicator("Average Directional Index (ADX)", overlay=false, timeframe="D", timeframe_gaps=true)

// Input for ADX period
int adxLengthInput             = input.int(14, title="ADX Period",             group = "ADX Settings")
int    adxSmoothingLengthInput = input.int(14, title="ADX Smoothing Period",     group = "ADX Settings")

directionalMovement(simple int length) =>
    float up             = ta.change(high)
    float down             = -ta.change(low)
    float truerange     = ta.rma(ta.tr, length)
    float plusDI         = fixnan(100 * ta.rma(up > down and up > 0 ? up : 0, length) / truerange)
    float minusDI         = fixnan(100 * ta.rma(down > up and down > 0 ? down : 0, length) / truerange)
    [plusDI, minusDI]

adx(simple int directionLength, simple int adxLength) =>
    [plusDI, minusDI]     = directionalMovement(directionLength)
    float sum             = plusDI + minusDI
    float adx             = 100 * ta.rma(math.abs(plusDI - minusDI) / (sum == 0 ? 1 : sum), adxLength)
    [adx, plusDI, minusDI]

[adx, plusDI, minusDI] = adx(adxSmoothingLengthInput, adxLengthInput)

// Plot the ADX line
plot(adx, title="ADX", color=color.blue)

// Plot +DI and -DI lines (for reference)
plot(plusDI, title="+DI", color=color.green)
plot(minusDI, title="-DI", color=color.red)

// Plot levels for better visualization
hline(20, "Low Level", color=color.gray)
hline(40, "High Level", color=color.gray)