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mathutil: add median utility #517

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merged 2 commits into from
May 16, 2024
Merged

mathutil: add median utility #517

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7a2c71a
add median utility
aalu1418 May 16, 2024
68ec12e
Med -> Median
aalu1418 May 16, 2024
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15 changes: 15 additions & 0 deletions pkg/utils/mathutil/mathutil.go
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@ package mathutil
import (
"fmt"
"math"
"slices"

"golang.org/x/exp/constraints"
)
Expand Down Expand Up @@ -49,3 +50,17 @@ func Avg[V constraints.Integer](arr ...V) (V, error) {

return total / V(len(arr)), nil
}

// Median mirrors implementation with generics: https://github.com/montanaflynn/stats/blob/249b5aaa10484bb7e8f3b866b0925aaebdac8170/median.go#L6
func Median[V constraints.Integer](arr ...V) (V, error) {
slices.Sort(arr)

l := len(arr)
if l == 0 {
return 0, fmt.Errorf("empty input")
}
if l%2 == 0 {
return Avg(arr[l/2-1 : l/2+1]...)
}
return arr[l/2], nil
}
17 changes: 17 additions & 0 deletions pkg/utils/mathutil/mathutil_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -56,3 +56,20 @@ func TestAvg(t *testing.T) {
r, err = Avg(a...)
assert.ErrorContains(t, err, "overflow: array len")
}

func TestMedian(t *testing.T) {
// happy path len = odd
v, err := Median(2, 1, 5, 4, 3)
assert.NoError(t, err)
assert.Equal(t, 3, v)

// happy path len = even
v, err = Median(10, 11, 1, 2)
assert.NoError(t, err)
assert.Equal(t, 6, v)

// zero input
v, err = Median[int]()
assert.Error(t, err)
assert.Equal(t, 0, v)
}
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