Function Geometric Mean Oscillator

//@version=2
study(title='Function Geometric Mean Oscillator', overlay=false)
//  ||-----------------------------------------------------------------------------------------||
//  ||---   As described here:
//  ||      http://www.investopedia.com/ask/answers/06/geometricmean.asp
//  ||-----------------------------------------------------------------------------------------||

src = input(close)
length = input(10)

f_gmo(_src, _length)=>
    _length_adjusted = _length < 1 ? 0 : _length
    _perc_change = change(_src) / _src
    _sum = 1
    for _i = 0 to (_length_adjusted)
        _sum := _sum * (1 + _perc_change[_i])
    _return = pow(_sum, (1 / _length_adjusted)) - 1

//plot(ema(src, length), color=color(gray, 0), linewidth=5)
plot(f_gmo(src, length), color=color(blue, 0), linewidth=1)
hline(0)