RSI on Bollinger Bands

//
// @author WebAction
// RSI on Bollinger Bands
// 
study(title = "RSI on Bollinger Bands", shorttitle="RSI+BB")
source = close
RSI_length = input(14, minval=1)
BB_length = input(50, minval=40, maxval=50)
BB_stdDev = input(2.1, minval=2.0, maxval=2.1)
HighlightBreaches=input(true, title="Highlight Oversold/Overbought?", type=bool)

rsi_s = rsi(source, RSI_length)
plot(rsi_s, color=black, linewidth=2)

bb_s = rsi_s
basis = sma(bb_s, BB_length)
dev = BB_stdDev * stdev(bb_s, BB_length)
upper = basis + dev
lower = basis - dev
plot(basis, color=red)
p1 = plot(upper, color=blue)
p2 = plot(lower, color=blue)
fill(p1,p2, blue)

b_color = (bb_s > upper) ? red : (bb_s < lower) ? green : na
bgcolor(HighlightBreaches ? b_color : na)