bbgo_origin/pkg/statistics/sharp.go

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package statistics
import (
"math"
"github.com/c9s/bbgo/pkg/types"
)
// Sharpe: Calcluates the sharpe ratio of access returns
//
// @param periods (int): Freq. of returns (252/365 for daily, 12 for monthy)
// @param annualize (bool): return annualize sharpe?
// @param smart (bool): return smart sharpe ratio
func Sharpe(returns types.Series, periods int, annualize bool, smart bool) float64 {
data := returns
num := data.Length()
if types.Lowest(data, num) >= 0 && types.Highest(data, num) > 1 {
data = types.PercentageChange(returns)
}
divisor := types.Stdev(data, data.Length(), 1)
if smart {
sum := 0.
coef := math.Abs(types.Correlation(data, types.Shift(data, 1), num-1))
for i := 1; i < num; i++ {
sum += float64(num-i) / float64(num) * math.Pow(coef, float64(i))
}
divisor = divisor * math.Sqrt(1.+2.*sum)
}
result := types.Mean(data) / divisor
if annualize {
return result * math.Sqrt(float64(periods))
}
return result
}