Relative Strength Index x2

study(title="Relative Strength Index x2", shorttitle="RSIx2")
src = close
len_fast = input(14, minval=1, title="Length")
len_slow = input(28, minval=1, title="Length")

up_fast = rma(max(change(src), 0), len_fast)
down_fast = rma(-min(change(src), 0), len_fast)
rsi_fast = down_fast == 0 ? 100 : up_fast == 0 ? 0 : 100 - (100 / (1 + up_fast / down_fast))

up_slow = rma(max(change(src), 0), len_slow)
down_slow = rma(-min(change(src), 0), len_slow)
rsi_slow = down_slow == 0 ? 100 : up_slow == 0 ? 0 : 100 - (100 / (1 + up_slow / down_slow))

diff = rsi_fast - rsi_slow + 50
diff_color = diff > diff[1] ? green : red

plot(diff, color=diff_color, style=columns, histbase=50, transp=80)
plot(rsi_slow, color=gray)
plot(rsi_fast, color=purple)

band1 = hline(70)
band0 = hline(30)
fill(band1, band0, color=purple, transp=90)