Standard Deviation

//@version=4
study("Standard Deviation",shorttitle="Stdev")
length = input(1024)
//Trading view method
a = sma(pow(close,2),length)
b = pow(sum(close,length),2)/pow(length,2)
c = sqrt(a - b)


//Tradingview method Confirm
d=stdev(close,length)

//Direct method
dev = close - sma(close, length)
variance = sum(pow(dev, 2), length) / (length -1)
e=sqrt(variance)

//Direction method function
sd(src, length) =>
    deviation = src - sma(src, length)
    variance = sum(pow(deviation, 2), length) / (length)
    sd=sqrt(variance)

//Tradingview method function
st_dev(Series, Period) =>
    E_1 = 0.0, E_2 = 0.0
    for i=0 to Period-1
        previousSeries = nz(Series[i])
        E_1 := E_1 + previousSeries
        E_2 := E_2 + previousSeries * previousSeries
    return = sqrt(E_2 / Period - (E_1 * E_1) / (Period * Period))

plot(c,color=color.red)
plot(d,color=color.green)
plot(e,color=color.aqua)