Add get_x and get_y vectorized functions (Point-only) (#37)

Co-authored-by: Benoit Bovy <benbovy@gmail.com>

docs/api.rst

@@ -17,6 +17,8 @@ Geography properties
    is_geography
    get_dimensions
    get_type_id
+   get_x
+   get_y
 
 .. _api_creation:
 

src/accessors-geog.cpp

@@ -26,6 +26,22 @@ PyObjectGeography convex_hull(PyObjectGeography a) {
     return make_py_geography(s2geog::s2_convex_hull(a_ptr));
 }
 
+double get_x(PyObjectGeography a) {
+    auto geog = a.as_geog_ptr();
+    if (geog->geog_type() != GeographyType::Point) {
+        throw py::value_error("Only Point geometries supported");
+    }
+    return s2geog::s2_x(geog->geog());
+}
+
+double get_y(PyObjectGeography a) {
+    auto geog = a.as_geog_ptr();
+    if (geog->geog_type() != GeographyType::Point) {
+        throw py::value_error("Only Point geometries supported");
+    }
+    return s2geog::s2_y(geog->geog());
+}
+
 double distance(PyObjectGeography a, PyObjectGeography b, double radius = EARTH_RADIUS_METERS) {
     const auto& a_index = a.as_geog_ptr()->geog_index();
     const auto& b_index = b.as_geog_ptr()->geog_index();
@@ -86,6 +102,32 @@ void init_accessors(py::module& m) {
 
     )pbdoc");
 
+    m.def("get_x",
+          py::vectorize(&get_x),
+          py::arg("a"),
+          R"pbdoc(
+        Returns the longitude value of the Point (in degrees).
+
+        Parameters
+        ----------
+        a: :py:class:`Geography` or array_like
+            Geography object(s).
+
+    )pbdoc");
+
+    m.def("get_y",
+          py::vectorize(&get_y),
+          py::arg("a"),
+          R"pbdoc(
+        Returns the latitude value of the Point (in degrees).
+
+        Parameters
+        ----------
+        a: :py:class:`Geography` or array_like
+            Geography object(s).
+
+    )pbdoc");
+
     m.def("distance",
           py::vectorize(&distance),
           py::arg("a"),

src/spherely.pyi

@@ -204,6 +204,11 @@ touches: _VFunc_Nin2_Nout1[Literal["touches"], bool, bool]
 covers: _VFunc_Nin2_Nout1[Literal["covers"], bool, bool]
 covered_by: _VFunc_Nin2_Nout1[Literal["covered_by"], bool, bool]
 
+# coords
+
+get_x: _VFunc_Nin1_Nout1[Literal["get_x"], float, np.float64]
+get_y: _VFunc_Nin1_Nout1[Literal["get_y"], float, np.float64]
+
 # geography accessors
 
 centroid: _VFunc_Nin1_Nout1[Literal["centroid"], PointGeography, PointGeography]

tests/test_accessors.py

@@ -84,6 +84,31 @@ def test_convex_hull(geog, expected) -> None:
     assert spherely.equals(actual, expected)
 
 
+def test_get_x_y() -> None:
+    # scalar
+    a = spherely.point(1.5, 2.6)
+    assert spherely.get_x(a) == pytest.approx(1.5, abs=1e-14)
+    assert spherely.get_y(a) == pytest.approx(2.6, abs=1e-14)
+
+    # array
+    arr = np.array([spherely.point(0, 1), spherely.point(1, 2), spherely.point(2, 3)])
+
+    actual = spherely.get_x(arr)
+    expected = np.array([0, 1, 2], dtype="float64")
+    np.testing.assert_allclose(actual, expected)
+
+    actual = spherely.get_y(arr)
+    expected = np.array([1, 2, 3], dtype="float64")
+    np.testing.assert_allclose(actual, expected)
+
+    # only points are supported
+    with pytest.raises(ValueError):
+        spherely.get_x(spherely.linestring([(0, 1), (1, 2)]))
+
+    with pytest.raises(ValueError):
+        spherely.get_y(spherely.linestring([(0, 1), (1, 2)]))
+
+
 @pytest.mark.parametrize(
     "geog_a, geog_b, expected",
     [