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May 3, 2023 21:10
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| <?php | |
| use Vector; | |
| use PHPUnit\Framework\Assert; | |
| expect()->extend('toBeWithin', function (float $expected, float $tolerance): void { | |
| $actual = $this->value; | |
| Assert::assertGreaterThanOrEqual($expected - $tolerance, $actual, "Expected {$actual} to be within {$tolerance} of {$expected}"); | |
| Assert::assertLessThanOrEqual($expected + $tolerance, $actual, "Expected {$actual} to be within {$tolerance} of {$expected}"); | |
| }); | |
| it('calculates cosine similarity of two identical vectors', function () { | |
| $vectorA = [1, 2, 3]; | |
| $vectorB = [1, 2, 3]; | |
| $similarity = Vector::cosineSimilarity($vectorA, $vectorB); | |
| expect($similarity)->toBeWithin(1.0, 0.0001); | |
| }); | |
| it('calculates cosine similarity of two orthogonal vectors', function () { | |
| $vectorA = [1, 0]; | |
| $vectorB = [0, 1]; | |
| $similarity = Vector::cosineSimilarity($vectorA, $vectorB); | |
| expect($similarity)->toBeWithin(0.0, 0.0001); | |
| }); | |
| it('calculates cosine similarity of two arbitrary vectors', function () { | |
| $vectorA = [1, 2, 3]; | |
| $vectorB = [4, 5, 6]; | |
| $similarity = Vector::cosineSimilarity($vectorA, $vectorB); | |
| expect($similarity)->toBeWithin(0.9746, 0.0001); | |
| }); | |
| it('throws an exception for vectors of different lengths', function () { | |
| $vectorA = [1, 2, 3]; | |
| $vectorB = [4, 5]; | |
| expect(fn() => Vector::cosineSimilarity($vectorA, $vectorB)) | |
| ->toThrow(InvalidArgumentException::class); | |
| }); | |
| it('throws an exception for vectors containing non-numeric elements', function () { | |
| $vectorA = [1, 2, 'foo']; | |
| $vectorB = [4, 5, 6]; | |
| expect(fn() => Vector::cosineSimilarity($vectorA, $vectorB)) | |
| ->toThrow(InvalidArgumentException::class); | |
| }); |
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| <?php | |
| class Vector | |
| { | |
| /** | |
| * Calculates the cosine similarity between two vectors. | |
| * | |
| * @param array $vectorA The first vector. | |
| * @param array $vectorB The second vector. | |
| * @return float The cosine similarity between the two vectors. | |
| * @throws \InvalidArgumentException If the vectors have different lengths or contain non-numeric values. | |
| */ | |
| public static function cosineSimilarity(array $vectorA, array $vectorB): float | |
| { | |
| if (! empty($vectorA) && count($vectorA) !== count($vectorB)) { | |
| throw new \InvalidArgumentException('Vectors must be of the same length'); | |
| } | |
| if (array_filter($vectorA, 'is_numeric') !== $vectorA || array_filter($vectorB, 'is_numeric') !== $vectorB) { | |
| throw new \InvalidArgumentException('Vectors must contain only numeric values'); | |
| } | |
| $dotProduct = static::dotProduct($vectorA, $vectorB); | |
| $magnitudeA = static::magnitude($vectorA); | |
| $magnitudeB = static::magnitude($vectorB); | |
| return $dotProduct / ($magnitudeA * $magnitudeB); | |
| } | |
| /** | |
| * Calculates the dot product of two vectors. | |
| * | |
| * @param array $vectorA The first vector. | |
| * @param array $vectorB The second vector. | |
| * @return float The dot product of the two vectors. | |
| */ | |
| private static function dotProduct(array $vectorA, array $vectorB): float | |
| { | |
| $result = 0; | |
| foreach ($vectorA as $key => $value) { | |
| $result += $value * $vectorB[$key]; | |
| } | |
| return $result; | |
| } | |
| /** | |
| * Calculates the magnitude of a vector. | |
| * | |
| * @param array $vector The vector for which to calculate the magnitude. | |
| * @return float The magnitude of the vector. | |
| */ | |
| private static function magnitude(array $vector): float | |
| { | |
| $result = 0; | |
| foreach ($vector as $value) { | |
| $result += $value ** 2; | |
| } | |
| return sqrt($result); | |
| } | |
| } |
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