Just Nifty RSI(9) v2

study(title="Just Nifty RSI(9)", shorttitle="RSI9")
src = close, len = input(9, minval=9, title="Length")
up = sma(max(change(src), 0), len)
down = sma(-min(change(src), 0), len)
rsi = down == 0 ? 100 : up == 0 ? 0 : 100 - (100 / (1 + up / down))
plot(rsi, color=blue)
band1 = hline(80)
band0 = hline(20)
fill(band1, band0, color=purple, transp=100)
plot(sma(rsi,9))
plot(sma (rsi,9) , color=red)