func/test: adding function and test for squeeze morph

Author: Luiskitsu

news/morphsqueeze.rst

@@ -4,7 +4,8 @@
 
 **Changed:**
 
-* Nothing changed
+* Added cubic and quadratic terms, as well as
+* squeeze_1 and squeeze_2 parameters
 
 **Deprecated:**
 

src/diffpy/morph/morphs/morphsqueeze.py

@@ -14,7 +14,7 @@ class MorphSqueeze(Morph):
     yinlabel = LABEL_GR  # This label need to change to be more generic
     xoutlabel = LABEL_RA  # This label need to change to be more generic
     youtlabel = LABEL_GR  # This label need to change to be more generic
-    parnames = ["squeeze"]
+    parnames = ["squeeze_1", "squeeze_2"]
 
     def morph(self, x_morph, y_morph, x_target, y_target):
         """Resample arrays onto the specified grid using a non-linear squeeze.
@@ -35,12 +35,17 @@ def morph(self, x_morph, y_morph, x_target, y_target):
         # Initialize the parent class to set up attributes
         Morph.morph(self, x_morph, y_morph, x_target, y_target)
 
-        # If squeeze is zero, return original output
-        if self.squeeze == 0:
+        # If squeeze_1 and squeeze_2 are zero, return original output
+        if self.squeeze_1 == 0 and self.squeeze_2 == 0:
             return self.xyallout
 
         # Compute new x positions using the non-linear squeeze transformation:
-        new_x = self.x_morph_in + self.squeeze * np.sin(self.x_morph_in)
+        new_x = (
+            self.x_morph_in
+            + self.squeeze_1 * self.x_morph_in**2
+            + self.squeeze_2 * self.x_morph_in**3
+        )
+
         self.x_morph_out = new_x
 
         # Interpolate the y-values at the new x positions.

tests/test_morphsqueeze.py

@@ -7,17 +7,18 @@
 class TestMorphSqueeze:
     @pytest.fixture
     def setup(self):
-        # Create a sine-wave for testing
-        self.x_morph = np.linspace(0, 2 * np.pi, 1000)
+        # Create data for testing
+        self.x_morph = np.linspace(0, 10, 1000)
         self.y_morph = np.sin(self.x_morph)
         self.x_target = self.x_morph.copy()
         self.y_target = self.y_morph.copy()
         return
 
     def test_no_squeeze(self, setup):
-        """When squeeze is zero, the input should be unchanged."""
+        """When both squeeze are zero, the input should be unchanged."""
         morph = MorphSqueeze()
-        morph.squeeze = 0.0
+        morph.squeeze_1 = 0.0
+        morph.squeeze_2 = 0.0
 
         x_morph, y_morph, x_target, y_target = morph(
             self.x_morph, self.y_morph, self.x_target, self.y_target
@@ -34,7 +35,9 @@ def test_morph_with_squeeze(self, setup):
         """Test that with a non-zero squeeze,
         x_morph is transformed non-linearly."""
         morph = MorphSqueeze()
-        morph.squeeze = 0.7
+        morph.squeeze_1 = -0.07
+        morph.squeeze_2 = 0.1
+
         x_new, y_new, x_target, y_target = morph(
             self.x_morph, self.y_morph, self.x_target, self.y_target
         )
@@ -43,9 +46,14 @@ def test_morph_with_squeeze(self, setup):
         assert np.allclose(self.y_target, y_target)
 
         # For this test, we expect:
-        # x_new = x_morph + squeeze_factor * sin(x_morph)
-        expected_x = self.x_morph + morph.squeeze * np.sin(self.x_morph)
-        expected_y = np.sin(expected_x)
+        # x_new = x_morph + squeeze_1 * x_morph ** 2 +
+        # squeeze_2 * x_morph ** 3
+        expected_x = (
+            self.x_morph
+            + morph.squeeze_1 * self.x_morph**2
+            + morph.squeeze_2 * self.x_morph**3
+        )
+        expected_y = np.interp(expected_x, self.x_morph, self.y_morph)
 
         # Allow for some tolerance because of numerical interpolation if used
         res = sum(np.fabs(expected_y - y_new))