Sorting, Searching, and Counting

Reference for sorting, searching, and counting operations.

These methods help you find values, sort arrays, and count occurrences.

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argmin()

public function argmin(?int $axis = null, bool $keepdims = false): int|NDArray

Index of minimum value over a given axis.

Parameters

Parameter	Type	Description
$axis	int|null	Axis along which to find argmin. If null, find argmin of flattened array. Optional. Default: null.
$keepdims	bool	If true, the reduced axis is retained with size 1. Optional. Default: false.

Returns

• int|NDArray - Scalar index if axis is null, otherwise an NDArray of indices.

Examples

$arr = NDArray::array([3, 1, 4, 1, 5]);

echo $arr->argmin();
// Output: 1 (first occurrence of 1)

$matrix = NDArray::array([
    [3, 1, 4],
    [1, 5, 9]
]);

print_r($matrix->argmin(axis: 0)->toArray());
// Output: [1, 0, 0]

print_r($matrix->argmin(axis: 1)->toArray());
// Output: [1, 0]

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argmax()

public function argmax(?int $axis = null, bool $keepdims = false): int|NDArray

Index of maximum value over a given axis.

Parameters

Parameter	Type	Description
$axis	int|null	Axis along which to find argmax. If null, find argmax of flattened array. Optional. Default: null.
$keepdims	bool	If true, the reduced axis is retained with size 1. Optional. Default: false.

Returns

• int|NDArray - Scalar index if axis is null, otherwise an NDArray of indices.

Examples

$arr = NDArray::array([3, 1, 4, 1, 5]);

echo $arr->argmax();
// Output: 4

$matrix = NDArray::array([
    [3, 1, 4],
    [1, 5, 9]
]);

print_r($matrix->argmax(axis: 0)->toArray());
// Output: [0, 1, 1]

print_r($matrix->argmax(axis: 1)->toArray());
// Output: [2, 2]

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sort()

public function sort(?int $axis = -1, SortKind $kind = SortKind::QuickSort): NDArray

Return a sorted copy of the array.

Parameters

Parameter	Type	Description
$axis	int|null	Axis along which to sort. If null, sort flattened data. Optional. Default: -1.
$kind	SortKind	Sorting algorithm. Optional. Default: SortKind::QuickSort.

Returns

• NDArray - Sorted array.

Examples

$arr = NDArray::array([3, 1, 4, 1, 5]);
$sorted = $arr->sort();
print_r($sorted->toArray());
// Output: [1, 1, 3, 4, 5]

$matrix = NDArray::array([[3, 1, 2], [6, 4, 5]]);
$sorted_rows = $matrix->sort(axis: 1);
print_r($sorted_rows->toArray());
// Output: [[1, 2, 3], [4, 5, 6]]

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argsort()

public function argsort(?int $axis = -1, SortKind $kind = SortKind::QuickSort): NDArray

Return indices that would sort the array.

Parameters

Parameter	Type	Description
$axis	int|null	Axis along which to argsort. If null, argsort flattened data. Optional. Default: -1.
$kind	SortKind	Sorting algorithm. Optional. Default: SortKind::QuickSort.

Returns

• NDArray - Int64 indices array.

Examples

$arr = NDArray::array([3, 1, 4, 1, 5]);
$indices = $arr->argsort();
print_r($indices->toArray());
// Output: [1, 3, 0, 2, 4]

// Use to sort
$sorted = $arr->take($indices);
print_r($sorted->toArray());
// Output: [1, 1, 3, 4, 5]

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topk()

public function topk(
    int $k,
    ?int $axis = -1,
    bool $largest = true,
    bool $sorted = true,
    SortKind $kind = SortKind::QuickSort
): array

Return top-k values and indices like PyTorch topk.

Parameters

Parameter	Type	Description
$k	int	Number of elements to select.
$axis	int|null	Axis along which to select. If null, flatten first. Optional. Default: -1.
$largest	bool	If true, select largest values; otherwise smallest values. Optional. Default: true.
$sorted	bool	If true, keep selected values sorted by rank. Optional. Default: true.
$kind	SortKind	Sorting algorithm. Optional. Default: SortKind::QuickSort.

Returns

• array - Array with keys 'values' (NDArray) and 'indices' (NDArray).

Raises

• InvalidArgumentException - If k < 0.

Examples

$arr = NDArray::array([3, 1, 4, 1, 5]);
$result = $arr->topk(3);

print_r($result['values']->toArray());
// Output: [5, 4, 3]

print_r($result['indices']->toArray());
// Output: [4, 2, 0]

// Smallest values
$result = $arr->topk(3, largest: false);
print_r($result['values']->toArray());
// Output: [1, 1, 3]

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bincount()

public function bincount(?int $minlength = null): NDArray

Count occurrences of non-negative integer values in flattened input.

Parameters

Parameter	Type	Description
$minlength	int|null	Minimum output length. Optional. Default: null.

Returns

• NDArray - Int64 counts array.

Raises

• InvalidArgumentException - If minlength < 0.

Examples

$arr = NDArray::array([0, 1, 1, 2, 2, 2, 3]);
$counts = $arr->bincount();
print_r($counts->toArray());
// Output: [1, 2, 3, 1]
// 0 appears 1 time, 1 appears 2 times, 2 appears 3 times, 3 appears 1 time

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Summary Table

Method	Description	Use Case
argmin()	Index of minimum	Find position of smallest value
argmax()	Index of maximum	Find position of largest value
sort()	Sort array	Order elements
argsort()	Indices to sort	Get sort order without sorting
topk()	Top k elements	Get largest/smallest k values
bincount()	Count occurrences	Histogram of integer values

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Next Steps

• Statistics
• Indexing Routines
• Mathematical Functions