├── README.md
├── cosine.go
└── cosine_test.go


/README.md:
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1 | # Cosine similarity in Go (Golang)
2 | Return the similarity (float64) of 2 []float64
3 | 


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/cosine.go:
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 1 | package cosine_similarity
 2 | 
 3 | import (
 4 | 	"errors"
 5 | 	"math"
 6 | )
 7 | 
 8 | func Cosine(a []float64, b []float64) (cosine float64, err error) {
 9 | 	count := 0
10 | 	length_a := len(a)
11 | 	length_b := len(b)
12 | 	if length_a > length_b {
13 | 		count = length_a
14 | 	} else {
15 | 		count = length_b
16 | 	}
17 | 	sumA := 0.0
18 | 	s1 := 0.0
19 | 	s2 := 0.0
20 | 	for k := 0; k < count; k++ {
21 | 		if k >= length_a {
22 | 			s2 += math.Pow(b[k], 2)
23 | 			continue
24 | 		}
25 | 		if k >= length_b {
26 | 			s1 += math.Pow(a[k], 2)
27 | 			continue
28 | 		}
29 | 		sumA += a[k] * b[k]
30 | 		s1 += math.Pow(a[k], 2)
31 | 		s2 += math.Pow(b[k], 2)
32 | 	}
33 | 	if s1 == 0 || s2 == 0 {
34 | 		return 0.0, errors.New("Vectors should not be null (all zeros)")
35 | 	}
36 | 	return sumA / (math.Sqrt(s1) * math.Sqrt(s2)), nil
37 | }
38 | 


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/cosine_test.go:
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 1 | package cosine_similarity
 2 | 
 3 | import (
 4 | 	"testing"
 5 | )
 6 | 
 7 | func TestCosine(t *testing.T) {
 8 | 
 9 | 	a := []float64{1, 1, 0, 0, 1}
10 | 	b := []float64{1, 1, 0, 0, 1}
11 | 	cos, err := Cosine(a, b)
12 | 	if err != nil {
13 | 		t.Error(err)
14 | 	}
15 | 	if cos < 0.99 {
16 | 		t.Error("Expected similarity of 1, got instead ", cos)
17 | 	}
18 | 	a = []float64{0, 1, 0, 1, 1}
19 | 	b = []float64{1, 0, 1, 0, 0}
20 | 	cos, err = Cosine(a, b)
21 | 	if err != nil {
22 | 		t.Error(err)
23 | 	}
24 | 	if cos != 0 {
25 | 		t.Error("Expected similarity of 0, got instead ", cos)
26 | 	}
27 | 	a = []float64{1, 1, 0}
28 | 	b = []float64{1, 0, 1}
29 | 	cos, err = Cosine(a, b)
30 | 	if err != nil {
31 | 		t.Error(err)
32 | 	}
33 | 	if cos < 0.49999 || cos > 0.5 {
34 | 		t.Error("Expected similarity of 0.5, got instead ", cos)
35 | 	}
36 | 	a = []float64{0, 1, 1, 1, 0}
37 | 	b = []float64{1, 0}
38 | 	cos, err = Cosine(a, b)
39 | 	if err != nil {
40 | 		t.Error(err)
41 | 	}
42 | 	if cos != 0 {
43 | 		t.Error("Expected similarity of 0, got instead ", cos)
44 | 	}
45 | }
46 | 


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