//@version=2
study("Standard Error Bands", overlay=true)
// Standard Error of the Estimate
beta(array,per) =>
    val1 = sum(n*array,per)-(per*sma(n,per)*sma(array,per))
    val2 = sum(pow(n,2),per)-(per*pow(sma(n,per),2))
    calcB = val1/val2

alpha(array,per) =>
    calcA = sma(array,per)-(beta(array,per)*sma(n,per))

see(array,per,mult,dir) =>
    lr = linreg(array,per,0)
    val1 = (sum(pow(array,2),per))-((alpha(array,per)*sum(array,per)))-((beta(array,per)*sum(n*array,per)))
    val2 = per - 2
    stde = sqrt(val1/val2)
    d = dir ? 1 : -1
    seband = lr + d * mult * stde
//plot(linreg(close,21))
plot(see(close,21,2,true))
plot(see(close,21,2,false))