Add heart target shape.

src/data_morph/shapes/factory.py

@@ -44,6 +44,7 @@ class ShapeFactory:
         'x': lines.XLines,
         'dots': points.DotsGrid,
         'down_parab': points.DownParabola,
+        'heart': points.Heart,
         'left_parab': points.LeftParabola,
         'scatter': points.Scatter,
         'right_parab': points.RightParabola,

src/data_morph/shapes/points.py

@@ -83,6 +83,54 @@ def __str__(self) -> str:
         return 'down_parab'
 
 
+class Heart(PointCollection):
+    """
+    Class for the heart shape.
+
+    .. plot::
+       :scale: 75
+       :caption:
+            This shape is generated using the panda dataset.
+
+        from data_morph.data.loader import DataLoader
+        from data_morph.shapes.points import Heart
+
+        _ = Heart(DataLoader.load_dataset('panda')).plot()
+
+    Parameters
+    ----------
+    dataset : Dataset
+        The starting dataset to morph into other shapes.
+
+    Notes
+    -----
+    The formula for the heart shape is inspired by
+    `Heart Curve <https://mathworld.wolfram.com/HeartCurve.html>`_:
+
+        Weisstein, Eric W. "Heart Curve." From `MathWorld <https://mathworld.wolfram.com/>`_
+        --A Wolfram Web Resource. https://mathworld.wolfram.com/HeartCurve.html
+    """
+
+    def __init__(self, dataset: Dataset) -> None:
+        x_bounds = dataset.data_bounds.x_bounds
+        y_bounds = dataset.data_bounds.y_bounds
+
+        x_shift = sum(x_bounds) / 2
+        y_shift = sum(y_bounds) / 2
+
+        t = np.linspace(-3, 3, num=80)
+
+        x = 16 * np.sin(t) ** 3
+        y = 13 * np.cos(t) - 5 * np.cos(2 * t) - 2 * np.cos(3 * t) - np.cos(4 * t)
+
+        # scale by the half the widest width of the heart
+        scale_factor = (x_bounds[1] - x_shift) / 16
+
+        super().__init__(
+            *np.stack([x * scale_factor + x_shift, y * scale_factor + y_shift], axis=1)
+        )
+
+
 class LeftParabola(PointCollection):
     """
     Class for the left parabola shape.

tests/shapes/test_points.py

@@ -25,7 +25,7 @@ def test_distance(self, shape, test_point, expected_distance):
         Test the distance() method parametrized by distance_test_cases
         (see conftest.py).
         """
-        assert pytest.approx(shape.distance(*test_point)) == expected_distance
+        assert pytest.approx(shape.distance(*test_point), abs=1e-5) == expected_distance
 
 
 class TestDotsGrid(PointsModuleTestBase):
@@ -67,6 +67,20 @@ def test_points_form_symmetric_grid(self, shape):
             assert row_midpoint == middle_row[point][1]
 
 
+class TestHeart(PointsModuleTestBase):
+    """Test the Heart class."""
+
+    shape_name = 'heart'
+    distance_test_cases = [
+        [(19.89946048, 54.82281916), 0.0],
+        [(10.84680454, 70.18556376), 0.0],
+        [(29.9971295, 67.66402445), 0.0],
+        [(27.38657942, 62.417184), 0.0],
+        [(20, 50), 4.567369],
+        [(10, 80), 8.564365],
+    ]
+
+
 class TestScatter(PointsModuleTestBase):
     """Test the Scatter class."""