API: Add set functions [Array API] (#619)

sparse/__init__.py

@@ -49,6 +49,8 @@
     roll,
     tril,
     triu,
+    unique_counts,
+    unique_values,
     where,
 )
 from ._dok import DOK
@@ -114,6 +116,8 @@
     "min",
     "max",
     "nanreduce",
+    "unique_counts",
+    "unique_values",
 ]
 
 __array_api_version__ = "2022.12"

sparse/_coo/__init__.py

@@ -20,6 +20,8 @@
     stack,
     tril,
     triu,
+    unique_counts,
+    unique_values,
     where,
 )
 from .core import COO, as_coo
@@ -49,4 +51,6 @@
     "result_type",
     "diagonal",
     "diagonalize",
+    "unique_counts",
+    "unique_values",
 ]

sparse/_coo/common.py

@@ -2,7 +2,7 @@
 import warnings
 from collections.abc import Iterable
 from functools import reduce
-from typing import Optional, Tuple
+from typing import NamedTuple, Optional, Tuple
 
 import numba
 
@@ -1059,6 +1059,106 @@ def clip(a, a_min=None, a_max=None, out=None):
     return a.clip(a_min, a_max)
 
 
+# Array API set functions
+
+
+class UniqueCountsResult(NamedTuple):
+    values: np.ndarray
+    counts: np.ndarray
+
+
+def unique_counts(x, /):
+    """
+    Returns the unique elements of an input array `x`, and the corresponding
+    counts for each unique element in `x`.
+
+    Parameters
+    ----------
+    x : COO
+        Input COO array. It will be flattened if it is not already 1-D.
+
+    Returns
+    -------
+    out : namedtuple
+        The result containing:
+        * values - The unique elements of an input array.
+        * counts - The corresponding counts for each unique element.
+
+    Raises
+    ------
+    ValueError
+        If the input array is in a different format than COO.
+
+    Examples
+    --------
+    >>> import sparse
+    >>> x = sparse.COO.from_numpy([1, 0, 2, 1, 2, -3])
+    >>> sparse.unique_counts(x)
+    UniqueCountsResult(values=array([-3,  0,  1,  2]), counts=array([1, 1, 2, 2]))
+    """
+    from .core import COO
+
+    if isinstance(x, scipy.sparse.spmatrix):
+        x = COO.from_scipy_sparse(x)
+    elif not isinstance(x, SparseArray):
+        raise ValueError(f"Input must be an instance of SparseArray, but it's {type(x)}.")
+    elif not isinstance(x, COO):
+        x = x.asformat(COO)
+
+    x = x.flatten()
+    values, counts = np.unique(x.data, return_counts=True)
+    if x.nnz < x.size:
+        values = np.concatenate([[x.fill_value], values])
+        counts = np.concatenate([[x.size - x.nnz], counts])
+        sorted_indices = np.argsort(values)
+        values[sorted_indices] = values.copy()
+        counts[sorted_indices] = counts.copy()
+
+    return UniqueCountsResult(values, counts)
+
+
+def unique_values(x, /):
+    """
+    Returns the unique elements of an input array `x`.
+
+    Parameters
+    ----------
+    x : COO
+        Input COO array. It will be flattened if it is not already 1-D.
+
+    Returns
+    -------
+    out : ndarray
+        The unique elements of an input array.
+
+    Raises
+    ------
+    ValueError
+        If the input array is in a different format than COO.
+
+    Examples
+    --------
+    >>> import sparse
+    >>> x = sparse.COO.from_numpy([1, 0, 2, 1, 2, -3])
+    >>> sparse.unique_values(x)
+    array([-3, 0, 1, 2])
+    """
+    from .core import COO
+
+    if isinstance(x, scipy.sparse.spmatrix):
+        x = COO.from_scipy_sparse(x)
+    elif not isinstance(x, SparseArray):
+        raise ValueError(f"Input must be an instance of SparseArray, but it's {type(x)}.")
+    elif not isinstance(x, COO):
+        x = x.asformat(COO)
+
+    x = x.flatten()
+    values = np.unique(x.data)
+    if x.nnz < x.size:
+        values = np.sort(np.concatenate([[x.fill_value], values]))
+    return values
+
+
 @numba.jit(nopython=True, nogil=True)
 def _compute_minmax_args(
     coords: np.ndarray,
@@ -1121,8 +1221,12 @@ def _arg_minmax_common(
 
     from .core import COO
 
-    if not isinstance(x, COO):
-        raise ValueError(f"Only COO arrays are supported but {type(x)} was passed.")
+    if isinstance(x, scipy.sparse.spmatrix):
+        x = COO.from_scipy_sparse(x)
+    elif not isinstance(x, SparseArray):
+        raise ValueError(f"Input must be an instance of SparseArray, but it's {type(x)}.")
+    elif not isinstance(x, COO):
+        x = x.asformat(COO)
 
     if not isinstance(axis, (int, type(None))):
         raise ValueError(f"`axis` must be `int` or `None`, but it's: {type(axis)}.")

sparse/tests/test_coo.py

@@ -1745,3 +1745,35 @@ def test_squeeze_validation(self):
 
         with pytest.raises(ValueError, match="Specified axis `0` has a size greater than one: 3"):
             s_arr.squeeze(0)
+
+
+class TestUnique:
+    arr = np.array([[0, 0, 1, 5, 3, 0], [1, 0, 4, 0, 3, 0], [0, 1, 0, 1, 1, 0]], dtype=np.int64)
+    arr_empty = np.zeros((5, 5))
+    arr_full = np.arange(1, 10)
+
+    @pytest.mark.parametrize("arr", [arr, arr_empty, arr_full])
+    @pytest.mark.parametrize("fill_value", [-1, 0, 1])
+    def test_unique_counts(self, arr, fill_value):
+        s_arr = sparse.COO.from_numpy(arr, fill_value)
+
+        result_values, result_counts = sparse.unique_counts(s_arr)
+        expected_values, expected_counts = np.unique(arr, return_counts=True)
+
+        np.testing.assert_equal(result_values, expected_values)
+        np.testing.assert_equal(result_counts, expected_counts)
+
+    @pytest.mark.parametrize("arr", [arr, arr_empty, arr_full])
+    @pytest.mark.parametrize("fill_value", [-1, 0, 1])
+    def test_unique_values(self, arr, fill_value):
+        s_arr = sparse.COO.from_numpy(arr, fill_value)
+
+        result = sparse.unique_values(s_arr)
+        expected = np.unique(arr)
+
+        np.testing.assert_equal(result, expected)
+
+    @pytest.mark.parametrize("func", [sparse.unique_counts, sparse.unique_values])
+    def test_input_validation(self, func):
+        with pytest.raises(ValueError, match=r"Input must be an instance of SparseArray"):
+            func(self.arr)