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|
package stats
import (
"math/rand"
"sort"
)
// Sample returns sample from input with replacement or without
func Sample(input Float64Data, takenum int, replacement bool) ([]float64, error) {
if input.Len() == 0 {
return nil, EmptyInputErr
}
length := input.Len()
if replacement {
result := Float64Data{}
rand.Seed(unixnano())
// In every step, randomly take the num for
for i := 0; i < takenum; i++ {
idx := rand.Intn(length)
result = append(result, input[idx])
}
return result, nil
} else if !replacement && takenum <= length {
rand.Seed(unixnano())
// Get permutation of number of indexies
perm := rand.Perm(length)
result := Float64Data{}
// Get element of input by permutated index
for _, idx := range perm[0:takenum] {
result = append(result, input[idx])
}
return result, nil
}
return nil, BoundsErr
}
// StableSample like stable sort, it returns samples from input while keeps the order of original data.
func StableSample(input Float64Data, takenum int) ([]float64, error) {
if input.Len() == 0 {
return nil, EmptyInputErr
}
length := input.Len()
if takenum <= length {
rand.Seed(unixnano())
perm := rand.Perm(length)
perm = perm[0:takenum]
// Sort perm before applying
sort.Ints(perm)
result := Float64Data{}
for _, idx := range perm {
result = append(result, input[idx])
}
return result, nil
}
return nil, BoundsErr
}
|
