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package stats
import "math"
// Entropy provides calculation of the entropy
func Entropy(input Float64Data) (float64, error) {
input, err := normalize(input)
if err != nil {
return math.NaN(), err
}
var result float64
for i := 0; i < input.Len(); i++ {
v := input.Get(i)
if v == 0 {
continue
}
result += (v * math.Log(v))
}
return -result, nil
}
func normalize(input Float64Data) (Float64Data, error) {
sum, err := input.Sum()
if err != nil {
return Float64Data{}, err
}
for i := 0; i < input.Len(); i++ {
input[i] = input[i] / sum
}
return input, nil
}
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